The formula for change in altitude with air pressure in the lower atmosphere (about to 35,000 feet) is:
P=Pb[1
Where:
Pb
TM,b
LM,b
h
hb
R
g0
M
The formula for change in altitude with air pressure in the lower atmosphere (about to 35,000 feet) is:
P=Pb[1
On Wed Aug 7 17:57:59 2024 Tom Kunich wrote:
The formula for change in altitude with air pressure in the lower atmosphere (about to 35,000 feet) is:
P=Pb[1
More posting problems:
P = Pb[ 1 - Lm,b/Tm,b(h - hb) ^ (g0M/R*Lb-1)
Where:
p = mass density (kg/m3)
Tb = standard temperature (K)
L = standard temperature lapse rate (see table below) (K/m) in ISA
h = height above sea level (geopotential meters)
R
On Wed, 07 Aug 2024 17:57:59 GMT, Tom Kunich <cyclintom@yahoo.com>
wrote:
The formula for change in altitude with air pressure in the lower atmosphere (about to 35,000 feet) is:
Nope. From what's left of your formula, I'll assume you're trying to calculate the air pressure at a given altitude. There is no *change*
in altitude involved. Looks like you lost all the Greek letter
symbols and formula symbols.
P=Pb[1
Where:
Pb
TM,b
LM,b
h
hb
R
g0
M
That unreadable mess should look something like these:
"Atmospheric Pressure Calculator" <https://calculator.academy/atmospheric-pressure-calculator/>
"Air Pressure at Altitude Calculator" <https://www.omnicalculator.com/physics/air-pressure-at-altitude>
Note that you need to know the barometric base pressure (Pb) at sea
level for such a calculation to work. It's NOT going to work if your
riding up or down a hill where the barometric pressure might change.
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
Google has just been found guilty of monopolistic practices and
will probably be forced to allow other search engines into the game.
What are you ever going to do when you cannot quote Google?
On Wed Aug 7 18:23:01 2024 Tom Kunich wrote:
Yee gods, Newshosting is a real piece of shit and Easynews doesn't even show the most recent posts.
R* = Universal Gas Constant (8.314498 N-m/m-k))
g0 = Gravitational accelleration (9.80665 m/s^2
M = Molar Mass of Earths air (0.0289664 kg/mol)
p = Mass density (slug/ft^3)
Tb = Standard Temperature
L = Standard Temperature Lapse Rate (K/ft)
h = Height above sea level (Garmin does not take tide into account)
As you can see,
the Garmin has to put a large percentage of their computational
power into calculating change in altitude=. This is particularly
difficult since below 10,000 feet, one foot of altitude chance
is about 1 mil-psi. The pressure detector doesn't have a whole
lot of surface are to detest changes which means that the
sensitivity is lower than ideal.
So in my opinion the Garmin does a pretty good job of calculating changes is altitide considering its limitations.
On Wed, 07 Aug 2024 17:57:59 GMT, Tom Kunich <cyclintom@yahoo.com>
wrote:
The formula for change in altitude with air pressure in the lower
atmosphere (about to 35,000 feet) is:
Nope. From what's left of your formula, I'll assume you're trying to calculate the air pressure at a given altitude. There is no *change*
in altitude involved. Looks like you lost all the Greek letter
symbols and formula symbols.
P=Pb[1
Where:
Pb
TM,b
LM,b
h
hb
R
g0
M
That unreadable mess should look something like these:
"Atmospheric Pressure Calculator" <https://calculator.academy/atmospheric-pressure-calculator/>
"Air Pressure at Altitude Calculator" <https://www.omnicalculator.com/physics/air-pressure-at-altitude>
Note that you need to know the barometric base pressure (Pb) at sea
level for such a calculation to work. It's NOT going to work if your
riding up or down a hill where the barometric pressure might change.
Jeff Liebermann <jeffl@cruzio.com> wrote:
On Wed, 07 Aug 2024 17:57:59 GMT, Tom Kunich <cyclintom@yahoo.com>
wrote:
The formula for change in altitude with air pressure in the lower
atmosphere (about to 35,000 feet) is:
Nope. From what's left of your formula, I'll assume you're trying to
calculate the air pressure at a given altitude. There is no *change*
in altitude involved. Looks like you lost all the Greek letter
symbols and formula symbols.
P=Pb[1
Where:
Pb
TM,b
LM,b
h
hb
R
g0
M
That unreadable mess should look something like these:
"Atmospheric Pressure Calculator"
<https://calculator.academy/atmospheric-pressure-calculator/>
"Air Pressure at Altitude Calculator"
<https://www.omnicalculator.com/physics/air-pressure-at-altitude>
Note that you need to know the barometric base pressure (Pb) at sea
level for such a calculation to work. It's NOT going to work if your
riding up or down a hill where the barometric pressure might change.
In fairness the 830 recalculates on start up every so often particularly if >its a changed location or it may well do so every time but dont watch it >start up in general.
Roger Merriman
On Wed, 07 Aug 2024 19:01:50 GMT, Tom Kunich <cyclintom@yahoo.com>
wrote:
Google has just been found guilty of monopolistic practices and
will probably be forced to allow other search engines into the game.
That's not the way I read the judgment.
"Justice Department lawyers argued that Google's monopoly enabled it
to charge advertisers artificially high prices while also enjoying the
luxury of not having to invest more time and money into improving the
quality of its search engine - a lax approach that hurt consumers."
All Google needs to do is add some useless features and lower their
prices on advertising. I see it as being much the same as when
Microsoft was judged to be a monopoly and nothing happened. In both
cases, it looks (to me) like the government reminding some large
companies that it's time to contribute to the campaigns of more
politicians. Start here and follow the money:
<https://www.opensecrets.org>
What are you ever going to do when you cannot quote Google?
I'm sloooowly switching to the Brave browser. It has it's own search
engine:
<https://search.brave.com>
So far, no major problems except maybe web sites that can't deal with
Brave's privacy features.
There are plenty other internet search sites available:
"23 Great Search Engines You Can Use Instead Of Google" <https://www.searchenginejournal.com/alternative-search-engines/271409/>
I've also been using various ChatBots for searching. Results have
been awful, but I'm not ready to give up on them yet.
I'm falling asleep at the keyboard. Good night.
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
On Thu, 08 Aug 2024 08:22:35 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:
On Thu, 08 Aug 2024 10:18:39 GMT, Roger Merriman <roger@sarlet.com>
wrote:
Jeff Liebermann <jeffl@cruzio.com> wrote:
On Wed, 07 Aug 2024 17:57:59 GMT, Tom Kunich <cyclintom@yahoo.com>
wrote:
The formula for change in altitude with air pressure in the lower
atmosphere (about to 35,000 feet) is:
Nope. From what's left of your formula, I'll assume you're trying to
calculate the air pressure at a given altitude. There is no *change*
in altitude involved. Looks like you lost all the Greek letter
symbols and formula symbols.
P=Pb[1
Where:
Pb
TM,b
LM,b
h
hb
R
g0
M
That unreadable mess should look something like these:
"Atmospheric Pressure Calculator"
<https://calculator.academy/atmospheric-pressure-calculator/>
"Air Pressure at Altitude Calculator"
<https://www.omnicalculator.com/physics/air-pressure-at-altitude>
Note that you need to know the barometric base pressure (Pb) at sea
level for such a calculation to work. It's NOT going to work if your
riding up or down a hill where the barometric pressure might change.
In fairness the 830 recalculates on start up every so often particularly if >>>its a changed location or it may well do so every time but dont watch it >>>start up in general.
Roger Merriman
Garmin works in mysterious ways. Garmin's self calibration algorithm
is a bit stranger than one might expect. For example: >><https://forums.garmin.com/sports-fitness/cycling/f/edge-830/174850/elevation-auto-calibration>
"Every time I start to record an activity on my Edge 830 I get this
message "Elevation calibrated to location" and immediately the
elevation number goes up by +/-12m out of the blue with me standing
still in the same spot.
The problem is that the elevation shown right before I press the
record button (before the "auto-calibration) is more accurate than the
one modified."
"The value is coming from the saved location that is near your
starting point."
I seem to recall reading somewhere that Garmin recommends calibration >>before starting on a ride. I'm too lazy to find where Garmin said
that.
However, that message is over 5 years old and the problem might have
been fixed long ago with a firmware update.
The barometric altimeter accuracy in the Garmin Edge 830 is specified
at +/-50 ft accuracy (which is better than the +/-400 ft accuracy for
the GPS). There's also a +/-10 ft error for reasons unknown: >><https://support.garmin.com/en-US/?faq=sFMkjQFdnZ99DcunfAue66>
"Elevation accuracy of +/-10 meters is for any given reading during an >>activity, not the total elevation gain/loss at the end of an
activity."
Very mysterious methinks.
Just how do these garmin gizmos work? Back when I worked on airplanes
the Altimeter measured the altitude above the home field. During
preflight, before engine start, the altimeter was set to "zero" and
during that flight measured height above the location where it was
set.
I believe in more modern times one calls the "Tower" and they give you
the altitude above sea level corrected by current temperature.
Where does the Garmin gets it base altitude from or is "0" simply the >altitude, and temperature, when/where you turn it on?
The basic system sounds much like my old airplane altimeter. But how
is atmospheric pressure due to temperature handled?
On Fri, 09 Aug 2024 17:36:48 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com>
wrote:
The basic system sounds much like my old airplane altimeter. But how
is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin,
has a built in temperature sensor and compensates internally.
<https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C
temperature accuracy. However, I can't tell if the pressure numbers
the sensor produces are pre-compensated internally in the sensor, or
if the pressure is calculated externally with a connected micro
controller. In other words, I don't know how Garmin does temperature
compensation.
The supplied code from Sparkfun shows that both pressure and
temperature are output by the sensor. However, it does not show any
external processing which would be needed to provide compensation.
<https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation.
I blundered across this explanation of how temperature compensations
works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?"
<https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is
interesting reading.
Calculating altitude with GPS seems to me to make more sense.
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com>
wrote:
The basic system sounds much like my old airplane altimeter. But how
is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin,
has a built in temperature sensor and compensates internally. ><https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C >temperature accuracy. However, I can't tell if the pressure numbers
the sensor produces are pre-compensated internally in the sensor, or
if the pressure is calculated externally with a connected micro
controller. In other words, I don't know how Garmin does temperature >compensation.
The supplied code from Sparkfun shows that both pressure and
temperature are output by the sensor. However, it does not show any
external processing which would be needed to provide compensation. ><https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation.
I blundered across this explanation of how temperature compensations
works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?" ><https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is
interesting reading.
Catrike Ryder <Soloman@old.bikers.org> wrote:
On Fri, 09 Aug 2024 17:36:48 -0700, Jeff Liebermann <jeffl@cruzio.com>It is how GPS without a barometric sensor do but its less accurate though
wrote:
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com>
wrote:
The basic system sounds much like my old airplane altimeter. But how
is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin,
has a built in temperature sensor and compensates internally.
<https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C
temperature accuracy. However, I can't tell if the pressure numbers
the sensor produces are pre-compensated internally in the sensor, or
if the pressure is calculated externally with a connected micro
controller. In other words, I don't know how Garmin does temperature
compensation.
The supplied code from Sparkfun shows that both pressure and
temperature are output by the sensor. However, it does not show any
external processing which would be needed to provide compensation.
<https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation.
I blundered across this explanation of how temperature compensations
works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?"
<https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is
interesting reading.
Calculating altitude with GPS seems to me to make more sense.
by how much and how much you care.
Im more likely to note the temperature with all the caveats though more >likely in winter.
Roger Merriman
On Fri, 09 Aug 2024 17:36:48 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com>
wrote:
The basic system sounds much like my old airplane altimeter. But how
is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin,
has a built in temperature sensor and compensates internally.
<https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C
temperature accuracy. However, I can't tell if the pressure numbers
the sensor produces are pre-compensated internally in the sensor, or
if the pressure is calculated externally with a connected micro
controller. In other words, I don't know how Garmin does temperature
compensation.
The supplied code from Sparkfun shows that both pressure and
temperature are output by the sensor. However, it does not show any
external processing which would be needed to provide compensation.
<https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation.
I blundered across this explanation of how temperature compensations
works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?"
<https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is
interesting reading.
Calculating altitude with GPS seems to me to make more sense.
On 8/10/2024 3:39 AM, Catrike Ryder wrote:
On Fri, 09 Aug 2024 17:36:48 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com>
wrote:
The basic system sounds much like my old airplane altimeter. But how
is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin,
has a built in temperature sensor and compensates internally.
<https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C
temperature accuracy. However, I can't tell if the pressure numbers
the sensor produces are pre-compensated internally in the sensor, or
if the pressure is calculated externally with a connected micro
controller. In other words, I don't know how Garmin does temperature
compensation.
The supplied code from Sparkfun shows that both pressure and
temperature are output by the sensor. However, it does not show any
external processing which would be needed to provide compensation.
<https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation.
I blundered across this explanation of how temperature compensations
works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?"
<https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is
interesting reading.
Calculating altitude with GPS seems to me to make more sense.
But not until crystal clocks, computing power and a
satellite network came together. See also ocean navigation
which was adequate before GPS but arguably better with it.
In our brave new world there aren't redundant systems and
one wonders about an EMP event for a Navy with no sextants...
On Sat, 10 Aug 2024 08:21:30 -0500, AMuzi <am@yellowjersey.org> wrote:
On 8/10/2024 3:39 AM, Catrike Ryder wrote:
On Fri, 09 Aug 2024 17:36:48 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com>
wrote:
The basic system sounds much like my old airplane altimeter. But how >>>>> is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin,
has a built in temperature sensor and compensates internally.
<https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C
temperature accuracy. However, I can't tell if the pressure numbers
the sensor produces are pre-compensated internally in the sensor, or
if the pressure is calculated externally with a connected micro
controller. In other words, I don't know how Garmin does temperature
compensation.
The supplied code from Sparkfun shows that both pressure and
temperature are output by the sensor. However, it does not show any
external processing which would be needed to provide compensation.
<https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation.
I blundered across this explanation of how temperature compensations
works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?"
<https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is
interesting reading.
Calculating altitude with GPS seems to me to make more sense.
But not until crystal clocks, computing power and a
satellite network came together. See also ocean navigation
which was adequate before GPS but arguably better with it.
In our brave new world there aren't redundant systems and
one wonders about an EMP event for a Navy with no sextants...
However, as soon as GPS became available, radio navigation was quickly recognized as being inadequate. I doubt Amelia Earhart would have been
lost at sea if she'd had GPS.
On Fri, 09 Aug 2024 17:36:48 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com>
wrote:
The basic system sounds much like my old airplane altimeter. But how
is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin,
has a built in temperature sensor and compensates internally. >><https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C >>temperature accuracy. However, I can't tell if the pressure numbers
the sensor produces are pre-compensated internally in the sensor, or
if the pressure is calculated externally with a connected micro
controller. In other words, I don't know how Garmin does temperature >>compensation.
The supplied code from Sparkfun shows that both pressure and
temperature are output by the sensor. However, it does not show any >>external processing which would be needed to provide compensation. >><https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation.
I blundered across this explanation of how temperature compensations
works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?" >><https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is >>interesting reading.
Calculating altitude with GPS seems to me to make more sense.
On 8/10/2024 8:58 AM, Catrike Ryder wrote:
On Sat, 10 Aug 2024 08:21:30 -0500, AMuzi <am@yellowjersey.org> wrote:
On 8/10/2024 3:39 AM, Catrike Ryder wrote:
On Fri, 09 Aug 2024 17:36:48 -0700, Jeff Liebermann <jeffl@cruzio.com> >>>> wrote:
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com>
wrote:
The basic system sounds much like my old airplane altimeter. But how >>>>>> is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin, >>>>> has a built in temperature sensor and compensates internally.
<https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C >>>>> temperature accuracy. However, I can't tell if the pressure numbers >>>>> the sensor produces are pre-compensated internally in the sensor, or >>>>> if the pressure is calculated externally with a connected micro
controller. In other words, I don't know how Garmin does temperature >>>>> compensation.
The supplied code from Sparkfun shows that both pressure and
temperature are output by the sensor. However, it does not show any >>>>> external processing which would be needed to provide compensation.
<https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation.
I blundered across this explanation of how temperature compensations >>>>> works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?"
<https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is
interesting reading.
Calculating altitude with GPS seems to me to make more sense.
But not until crystal clocks, computing power and a
satellite network came together. See also ocean navigation
which was adequate before GPS but arguably better with it.
In our brave new world there aren't redundant systems and
one wonders about an EMP event for a Navy with no sextants...
However, as soon as GPS became available, radio navigation was quickly
recognized as being inadequate. I doubt Amelia Earhart would have been
lost at sea if she'd had GPS.
You don't know that. And I don't know it wasn't.
The probable debris site is near Howland Island, her
intended destination. Her last radio message to Navy at
Howland was 'low on fuel'. It may well have been a tragic
arithmetic error in fuel rate. Or not.
On 8/10/2024 12:10 PM, Catrike Ryder wrote:
On Sat, 10 Aug 2024 10:56:30 -0500, AMuzi <am@yellowjersey.org> wrote:
On 8/10/2024 8:58 AM, Catrike Ryder wrote:
On Sat, 10 Aug 2024 08:21:30 -0500, AMuzi <am@yellowjersey.org> wrote: >>>>
On 8/10/2024 3:39 AM, Catrike Ryder wrote:
On Fri, 09 Aug 2024 17:36:48 -0700, Jeff Liebermann <jeffl@cruzio.com> >>>>>> wrote:
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com> >>>>>>> wrote:
The basic system sounds much like my old airplane altimeter. But how >>>>>>>> is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin, >>>>>>> has a built in temperature sensor and compensates internally.
<https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C >>>>>>> temperature accuracy. However, I can't tell if the pressure numbers >>>>>>> the sensor produces are pre-compensated internally in the sensor, or >>>>>>> if the pressure is calculated externally with a connected micro
controller. In other words, I don't know how Garmin does temperature >>>>>>> compensation.
The supplied code from Sparkfun shows that both pressure and
temperature are output by the sensor. However, it does not show any >>>>>>> external processing which would be needed to provide compensation. >>>>>>> <https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation. >>>>>>>
I blundered across this explanation of how temperature compensations >>>>>>> works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?"
<https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is >>>>>>> interesting reading.
Calculating altitude with GPS seems to me to make more sense.
But not until crystal clocks, computing power and a
satellite network came together. See also ocean navigation
which was adequate before GPS but arguably better with it.
In our brave new world there aren't redundant systems and
one wonders about an EMP event for a Navy with no sextants...
However, as soon as GPS became available, radio navigation was quickly >>>> recognized as being inadequate. I doubt Amelia Earhart would have been >>>> lost at sea if she'd had GPS.
You don't know that. And I don't know it wasn't.
The probable debris site is near Howland Island, her
intended destination. Her last radio message to Navy at
Howland was 'low on fuel'. It may well have been a tragic
arithmetic error in fuel rate. Or not.
It was known that they were having navigation problems.
Thanks I did not know that.
On Sat, 10 Aug 2024 10:56:30 -0500, AMuzi <am@yellowjersey.org> wrote:
On 8/10/2024 8:58 AM, Catrike Ryder wrote:
On Sat, 10 Aug 2024 08:21:30 -0500, AMuzi <am@yellowjersey.org> wrote:
On 8/10/2024 3:39 AM, Catrike Ryder wrote:
On Fri, 09 Aug 2024 17:36:48 -0700, Jeff Liebermann <jeffl@cruzio.com> >>>>> wrote:
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com>
wrote:
The basic system sounds much like my old airplane altimeter. But how >>>>>>> is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin, >>>>>> has a built in temperature sensor and compensates internally.
<https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C >>>>>> temperature accuracy. However, I can't tell if the pressure numbers >>>>>> the sensor produces are pre-compensated internally in the sensor, or >>>>>> if the pressure is calculated externally with a connected micro
controller. In other words, I don't know how Garmin does temperature >>>>>> compensation.
The supplied code from Sparkfun shows that both pressure and
temperature are output by the sensor. However, it does not show any >>>>>> external processing which would be needed to provide compensation. >>>>>> <https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation. >>>>>>
I blundered across this explanation of how temperature compensations >>>>>> works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?"
<https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is
interesting reading.
Calculating altitude with GPS seems to me to make more sense.
But not until crystal clocks, computing power and a
satellite network came together. See also ocean navigation
which was adequate before GPS but arguably better with it.
In our brave new world there aren't redundant systems and
one wonders about an EMP event for a Navy with no sextants...
However, as soon as GPS became available, radio navigation was quickly
recognized as being inadequate. I doubt Amelia Earhart would have been
lost at sea if she'd had GPS.
You don't know that. And I don't know it wasn't.
The probable debris site is near Howland Island, her
intended destination. Her last radio message to Navy at
Howland was 'low on fuel'. It may well have been a tragic
arithmetic error in fuel rate. Or not.
It was known that they were having navigation problems.
On 8/10/2024 12:21 PM, Jeff Liebermann wrote:
GPS is far more accurate measuring 2D surface distances than 3D
measuring altitude.
"Grade, Elevation, and GPS Accuracy FAQ"
<https://support.ridewithgps.com/hc/en-us/articles/4419010957467-Grade-Elevation-and-GPS-Accuracy-FAQ>
Garmin rates their GPS elevation accuracy at +/-400 ft and their
barometric elevation accuracy at +/-50 ft.
If anyone wants me to explain why in excruciating detail if anyone is
interested. The short version is that GPS works by measuring the
Doppler shifts produced by multiple satellites across the sky. The
motion of the satellite has to be mostly toward or away from the GPS
receiver. For altitude, that happens best when the satellites are
near the horizon. A satellite directly overhead does not move toward
or away from the GPS receiver and is therefore useless for computing
altitude. Since the horizon tends to be cluttered with mountains,
trees, buildings, reflections etc, the signals from the best
positioned satellites can't be used. Just to make things difficult,
the better GPS antennas are designed to suppress ground reflections
which makes using low elevation satellites even more difficult to use.
IIRC, Jobst explained that with some trigonometric detail many years ago.
And it's all irrelevant for Florida bike paths.
I'll note that the instruments probably need to have temperature
compensation built in. I was once given a small portable electronic >altimeter/barometer. Today, because of these discussions, I played with
it a bit. I calibrated it at my home (where I know the altitude based on
USGS maps, which is confirmed by my car's GPS) and drove about 8 miles
away. There I left it in the parked car for a couple hours.
The sun was shining (despite this being NE Ohio!) and heated up the
car's interior and the altimeter. When I returned, the altimeter
displayed nearly 100 feet less altitude than when I first arrived.
I wonder how temperature compensation is or was handled for the old >mechanical aneroid barometers.
On Sat, 10 Aug 2024 08:54:20 GMT, Roger Merriman <roger@sarlet.com>
wrote:
Catrike Ryder <Soloman@old.bikers.org> wrote:
On Fri, 09 Aug 2024 17:36:48 -0700, Jeff Liebermann <jeffl@cruzio.com>It is how GPS without a barometric sensor do but its less accurate though >> by how much and how much you care.
wrote:
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com>
wrote:
The basic system sounds much like my old airplane altimeter. But how >>>>> is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin,
has a built in temperature sensor and compensates internally.
<https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C
temperature accuracy. However, I can't tell if the pressure numbers
the sensor produces are pre-compensated internally in the sensor, or
if the pressure is calculated externally with a connected micro
controller. In other words, I don't know how Garmin does temperature
compensation.
The supplied code from Sparkfun shows that both pressure and
temperature are output by the sensor. However, it does not show any
external processing which would be needed to provide compensation.
<https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation.
I blundered across this explanation of how temperature compensations
works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?"
<https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is
interesting reading.
Calculating altitude with GPS seems to me to make more sense.
Im more likely to note the temperature with all the caveats though more >> likely in winter.
Roger Merriman
GPS altitude calculation should be more accurate if it can read four satellites.
********************************
Is GPS Accurate for Altitude?
Private Pilot
Made Easy
There is no such thing as a perfect system, and GPS is no exception.
When it works, it is highly accurate. In fact, there are currently
plans to eventually replace conventional aviation navigation aids with
GPS (GBAS) landing systems.
However, GPS altitude can be affected by the following:
Ionospheric errors The Earth is surrounded by layers of a dense atmosphere that change in size and thickness depending on solar
activity and the time of day. This can cause minor altitude errors.
Clock errors GPS clocks are phenomenally However, even a
minuscule disruption to their timing can cause errors. This doesnt
happen often, and GPS receivers normally discard a timing signal they recognize as erroneous.
Rounding errors Generally, these errors are small, but in an
aircraft, precision matters.
Satellite signal loss Like any piece of electrical equipment, Satellites do sometimes stop working or are rebooted. For a GPS to
provide accurate altitude readings, it needs multiple satellites,
normally four. If the fourth drops out at a critical time, this could
cause issues.
https://pilotinstitute.com/altimeter-vs-gps-altitude/
*********************************
I understand that using four satellites, time errors can be
compensated, and four satellites are required for altitude
calculations anyway. It seems to me that the biggest problem with GPS altitude is possible loss of satellite reception, which is a serious
issue for airplanes, but not such a big deal for land and sea
operations. Why Garmin and other land based GPS systems don't use GPS altitude is a mystery to me.
Catrike Ryder <Soloman@old.bikers.org> wrote:
On Sat, 10 Aug 2024 08:54:20 GMT, Roger Merriman <roger@sarlet.com>All of the big three ie Garmin-Wahoo-Hammerhead on there upper end devices >all have barometric sensors for improved accuracy, Im assuming that while >GPS Altitude is indeed more accurate flying or sailing, this isnt the same >cycling with sky cover and undulating land.
wrote:
Catrike Ryder <Soloman@old.bikers.org> wrote:
On Fri, 09 Aug 2024 17:36:48 -0700, Jeff Liebermann <jeffl@cruzio.com> >>>> wrote:It is how GPS without a barometric sensor do but it?s less accurate though >>> by how much and how much you care.
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com>
wrote:
The basic system sounds much like my old airplane altimeter. But how >>>>>> is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin, >>>>> has a built in temperature sensor and compensates internally.
<https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C >>>>> temperature accuracy. However, I can't tell if the pressure numbers >>>>> the sensor produces are pre-compensated internally in the sensor, or >>>>> if the pressure is calculated externally with a connected micro
controller. In other words, I don't know how Garmin does temperature >>>>> compensation.
The supplied code from Sparkfun shows that both pressure and
temperature are output by the sensor. However, it does not show any >>>>> external processing which would be needed to provide compensation.
<https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation.
I blundered across this explanation of how temperature compensations >>>>> works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?"
<https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is
interesting reading.
Calculating altitude with GPS seems to me to make more sense.
I?m more likely to note the temperature with all the caveat?s though more >>> likely in winter.
Roger Merriman
GPS altitude calculation should be more accurate if it can read four
satellites.
********************************
Is GPS Accurate for Altitude?
Private Pilot
Made Easy
There is no such thing as a ?perfect? system, and GPS is no exception.
When it works, it is highly accurate. In fact, there are currently
plans to eventually replace conventional aviation navigation aids with
GPS (GBAS) landing systems.
However, GPS altitude can be affected by the following: ?
Ionospheric errors ? The Earth is surrounded by layers of a dense
atmosphere that change in size and thickness depending on solar
activity and the time of day. This can cause minor altitude errors.
Clock errors ? GPS clocks are phenomenally However, even a
minuscule disruption to their timing can cause errors. This doesn?t
happen often, and GPS receivers normally discard a timing signal they
recognize as erroneous.
Rounding errors ? Generally, these errors are small, but in an
aircraft, precision matters.
Satellite signal loss ? Like any piece of electrical equipment,
Satellites do sometimes stop working or are rebooted. For a GPS to
provide accurate altitude readings, it needs multiple satellites,
normally four. If the fourth drops out at a critical time, this could
cause issues.
https://pilotinstitute.com/altimeter-vs-gps-altitude/
*********************************
I understand that using four satellites, time errors can be
compensated, and four satellites are required for altitude
calculations anyway. It seems to me that the biggest problem with GPS
altitude is possible loss of satellite reception, which is a serious
issue for airplanes, but not such a big deal for land and sea
operations. Why Garmin and other land based GPS systems don't use GPS
altitude is a mystery to me.
Ie clearly must be some engineering reason to do so, most likely the above.
Roger Merriman
On Sun, 11 Aug 2024 07:14:17 -0400, Catrike Ryder
<Soloman@old.bikers.org> wrote:
On Sun, 11 Aug 2024 10:24:10 GMT, Roger Merriman <roger@sarlet.com>
wrote:
Catrike Ryder <Soloman@old.bikers.org> wrote:
On Sat, 10 Aug 2024 08:54:20 GMT, Roger Merriman <roger@sarlet.com>All of the big three ie Garmin-Wahoo-Hammerhead on there upper end devices >>>all have barometric sensors for improved accuracy, Im assuming that while >>>GPS Altitude is indeed more accurate flying or sailing, this isnt the same >>>cycling with sky cover and undulating land.
wrote:
Catrike Ryder <Soloman@old.bikers.org> wrote:
On Fri, 09 Aug 2024 17:36:48 -0700, Jeff Liebermann <jeffl@cruzio.com> >>>>>> wrote:It is how GPS without a barometric sensor do but it?s less accurate though
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com> >>>>>>> wrote:
The basic system sounds much like my old airplane altimeter. But how >>>>>>>> is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin, >>>>>>> has a built in temperature sensor and compensates internally.
<https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C >>>>>>> temperature accuracy. However, I can't tell if the pressure numbers >>>>>>> the sensor produces are pre-compensated internally in the sensor, or >>>>>>> if the pressure is calculated externally with a connected micro
controller. In other words, I don't know how Garmin does temperature >>>>>>> compensation.
The supplied code from Sparkfun shows that both pressure and
temperature are output by the sensor. However, it does not show any >>>>>>> external processing which would be needed to provide compensation. >>>>>>> <https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation. >>>>>>>
I blundered across this explanation of how temperature compensations >>>>>>> works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?"
<https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is >>>>>>> interesting reading.
Calculating altitude with GPS seems to me to make more sense.
by how much and how much you care.
I?m more likely to note the temperature with all the caveat?s though more >>>>> likely in winter.
Roger Merriman
GPS altitude calculation should be more accurate if it can read four
satellites.
********************************
Is GPS Accurate for Altitude?
Private Pilot
Made Easy
There is no such thing as a ?perfect? system, and GPS is no exception. >>>> When it works, it is highly accurate. In fact, there are currently
plans to eventually replace conventional aviation navigation aids with >>>> GPS (GBAS) landing systems.
However, GPS altitude can be affected by the following: ?
Ionospheric errors ? The Earth is surrounded by layers of a dense
atmosphere that change in size and thickness depending on solar
activity and the time of day. This can cause minor altitude errors.
Clock errors ? GPS clocks are phenomenally However, even a
minuscule disruption to their timing can cause errors. This doesn?t
happen often, and GPS receivers normally discard a timing signal they
recognize as erroneous.
Rounding errors ? Generally, these errors are small, but in an
aircraft, precision matters.
Satellite signal loss ? Like any piece of electrical equipment,
Satellites do sometimes stop working or are rebooted. For a GPS to
provide accurate altitude readings, it needs multiple satellites,
normally four. If the fourth drops out at a critical time, this could
cause issues.
https://pilotinstitute.com/altimeter-vs-gps-altitude/
*********************************
I understand that using four satellites, time errors can be
compensated, and four satellites are required for altitude
calculations anyway. It seems to me that the biggest problem with GPS >>>> altitude is possible loss of satellite reception, which is a serious
issue for airplanes, but not such a big deal for land and sea
operations. Why Garmin and other land based GPS systems don't use GPS
altitude is a mystery to me.
Ie clearly must be some engineering reason to do so, most likely the above. >>>
Roger Merriman
I don't pay any attention to altitude on my rides, although it is
recorded on my Garmin computer. There are 30/40 foot variations in
maximum altitude when I compare identical rides, so whatever method
the computer uses is worthless.
I tended to ride in the early morning before going to work and so used
a simple - count the revolutions - speedometer to measurer speed and
distance and simply calculate the average speed for the morning's
ride. The fact that I got up a 1 mile long hill a bit faster, or
slower, was (to me) ]meaningless, it was the total time for the
entire ride divided by the miles traveled.
GPS altitude calculation should be more accurate if it can read four >satellites.
On 8/10/2024 12:21 PM, Jeff Liebermann wrote:
GPS is far more accurate measuring 2D surface distances than
3D measuring altitude. "Grade, Elevation, and GPS Accuracy
FAQ" <https://support.ridewithgps.com/hc/en-us/articles/4419010957467-Grade-Elevation-and-GPS-Accuracy-FAQ>
Garmin rates their GPS elevation accuracy at +/-400 ft and
their barometric elevation accuracy at +/-50 ft.
If anyone wants me to explain why in excruciating detail if
anyone is interested. The short version is that GPS works by
measuring the Doppler shifts produced by multiple satellites
across the sky. The motion of the satellite has to be mostly
toward or away from the GPS receiver. For altitude, that
happens best when the satellites are near the horizon. A
satellite directly overhead does not move toward or away from
the GPS receiver and is therefore useless for computing
altitude. Since the horizon tends to be cluttered with
mountains, trees, buildings, reflections etc, the signals from
the best positioned satellites can't be used. Just to make
things difficult, the better GPS antennas are designed to
suppress ground reflections which makes using low elevation
satellites even more difficult to use.
IIRC, Jobst explained that with some trigonometric detail many
years ago.
And it's all irrelevant for Florida bike paths.
On Sun, 11 Aug 2024 18:49:09 +0700, John B. <slocombjb@gmail.com>
wrote:
On Sun, 11 Aug 2024 07:14:17 -0400, Catrike Ryder
<Soloman@old.bikers.org> wrote:
On Sun, 11 Aug 2024 10:24:10 GMT, Roger Merriman <roger@sarlet.com>
wrote:
Catrike Ryder <Soloman@old.bikers.org> wrote:
On Sat, 10 Aug 2024 08:54:20 GMT, Roger Merriman <roger@sarlet.com>All of the big three ie Garmin-Wahoo-Hammerhead on there upper end devices >>>> all have barometric sensors for improved accuracy, Im assuming that while
wrote:
Catrike Ryder <Soloman@old.bikers.org> wrote:
On Fri, 09 Aug 2024 17:36:48 -0700, Jeff Liebermann <jeffl@cruzio.com> >>>>>>> wrote:It is how GPS without a barometric sensor do but it?s less accurate though
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com> >>>>>>>> wrote:
The basic system sounds much like my old airplane altimeter. But how >>>>>>>>> is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin, >>>>>>>> has a built in temperature sensor and compensates internally.
<https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C >>>>>>>> temperature accuracy. However, I can't tell if the pressure numbers >>>>>>>> the sensor produces are pre-compensated internally in the sensor, or >>>>>>>> if the pressure is calculated externally with a connected micro >>>>>>>> controller. In other words, I don't know how Garmin does temperature >>>>>>>> compensation.
The supplied code from Sparkfun shows that both pressure and
temperature are output by the sensor. However, it does not show any >>>>>>>> external processing which would be needed to provide compensation. >>>>>>>> <https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation. >>>>>>>>
I blundered across this explanation of how temperature compensations >>>>>>>> works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?"
<https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is >>>>>>>> interesting reading.
Calculating altitude with GPS seems to me to make more sense.
by how much and how much you care.
I?m more likely to note the temperature with all the caveat?s though more
likely in winter.
Roger Merriman
GPS altitude calculation should be more accurate if it can read four >>>>> satellites.
********************************
Is GPS Accurate for Altitude?
Private Pilot
Made Easy
There is no such thing as a ?perfect? system, and GPS is no exception. >>>>> When it works, it is highly accurate. In fact, there are currently
plans to eventually replace conventional aviation navigation aids with >>>>> GPS (GBAS) landing systems.
However, GPS altitude can be affected by the following: ?
Ionospheric errors ? The Earth is surrounded by layers of a dense
atmosphere that change in size and thickness depending on solar
activity and the time of day. This can cause minor altitude errors.
Clock errors ? GPS clocks are phenomenally However, even a
minuscule disruption to their timing can cause errors. This doesn?t
happen often, and GPS receivers normally discard a timing signal they >>>>> recognize as erroneous.
Rounding errors ? Generally, these errors are small, but in an
aircraft, precision matters.
Satellite signal loss ? Like any piece of electrical equipment,
Satellites do sometimes stop working or are rebooted. For a GPS to
provide accurate altitude readings, it needs multiple satellites,
normally four. If the fourth drops out at a critical time, this could >>>>> cause issues.
https://pilotinstitute.com/altimeter-vs-gps-altitude/
*********************************
I understand that using four satellites, time errors can be
compensated, and four satellites are required for altitude
calculations anyway. It seems to me that the biggest problem with GPS >>>>> altitude is possible loss of satellite reception, which is a serious >>>>> issue for airplanes, but not such a big deal for land and sea
operations. Why Garmin and other land based GPS systems don't use GPS >>>>> altitude is a mystery to me.
GPS Altitude is indeed more accurate flying or sailing, this isnt the same
cycling with sky cover and undulating land.
Ie clearly must be some engineering reason to do so, most likely the above.
Roger Merriman
I don't pay any attention to altitude on my rides, although it is
recorded on my Garmin computer. There are 30/40 foot variations in
maximum altitude when I compare identical rides, so whatever method
the computer uses is worthless.
I tended to ride in the early morning before going to work and so used
a simple - count the revolutions - speedometer to measurer speed and
distance and simply calculate the average speed for the morning's
ride. The fact that I got up a 1 mile long hill a bit faster, or
slower, was (to me) ]meaningless, it was the total time for the
entire ride divided by the miles traveled.
My Garmin computer counts the wheel revolutions to get speed and
distance, although it will use GPS if there is no wheel sensor or if
it fails. The computer also uses GPS to set the wheel circumference.
Total distance and average speed is also what I consider the most
significant data. Strava collects individual segment times so riders
can compare themselves with other riders, but I think that's silly.
Unless a person is among the best professional bike racers, there's
always going to be someone who is faster. It's just a matter of
picking who you're going to race against. Pick slower competitors and
you will win, pick faster competitors and you will lose. I only race
against myself.
On Sat, 10 Aug 2024 14:12:12 -0400,
Frank Krygowski <frkrygow@sbcglobal.net> wrote:
On 8/10/2024 12:21 PM, Jeff Liebermann wrote:
GPS is far more accurate measuring 2D surface distances than
3D measuring altitude. "Grade, Elevation, and GPS Accuracy
FAQ"
<https://support.ridewithgps.com/hc/en-us/articles/4419010957467-Grade-Elevation-and-GPS-Accuracy-FAQ>
Garmin rates their GPS elevation accuracy at +/-400 ft and
their barometric elevation accuracy at +/-50 ft.
If anyone wants me to explain why in excruciating detail if
anyone is interested. The short version is that GPS works by
measuring the Doppler shifts produced by multiple satellites
across the sky. The motion of the satellite has to be mostly
toward or away from the GPS receiver. For altitude, that
happens best when the satellites are near the horizon. A
satellite directly overhead does not move toward or away from
the GPS receiver and is therefore useless for computing
altitude. Since the horizon tends to be cluttered with
mountains, trees, buildings, reflections etc, the signals from
the best positioned satellites can't be used. Just to make
things difficult, the better GPS antennas are designed to
suppress ground reflections which makes using low elevation
satellites even more difficult to use.
Yep, and nice explanation.
IIRC, Jobst explained that with some trigonometric detail many
years ago.
And it's all irrelevant for Florida bike paths.
LOL Reminds me of a tandem rally in Sebring a few years ago. At
one point we rode with a couple from Ft. Lauderdale and had a hard
time keeping straight faces when they complained about the hills.
Catrike Ryder <Soloman@old.bikers.org> wrote:
On Sun, 11 Aug 2024 18:49:09 +0700, John B. <slocombjb@gmail.com>Average speed is personally one of the least useful metrics, as a gravel
wrote:
On Sun, 11 Aug 2024 07:14:17 -0400, Catrike Ryder
<Soloman@old.bikers.org> wrote:
On Sun, 11 Aug 2024 10:24:10 GMT, Roger Merriman <roger@sarlet.com>
wrote:
Catrike Ryder <Soloman@old.bikers.org> wrote:
On Sat, 10 Aug 2024 08:54:20 GMT, Roger Merriman <roger@sarlet.com> >>>>>> wrote:All of the big three ie Garmin-Wahoo-Hammerhead on there upper end devices
Catrike Ryder <Soloman@old.bikers.org> wrote:
On Fri, 09 Aug 2024 17:36:48 -0700, Jeff Liebermann <jeffl@cruzio.com> >>>>>>>> wrote:It is how GPS without a barometric sensor do but it?s less accurate though
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com> >>>>>>>>> wrote:
The basic system sounds much like my old airplane altimeter. But how >>>>>>>>>> is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin, >>>>>>>>> has a built in temperature sensor and compensates internally. >>>>>>>>> <https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C >>>>>>>>> temperature accuracy. However, I can't tell if the pressure numbers >>>>>>>>> the sensor produces are pre-compensated internally in the sensor, or >>>>>>>>> if the pressure is calculated externally with a connected micro >>>>>>>>> controller. In other words, I don't know how Garmin does temperature >>>>>>>>> compensation.
The supplied code from Sparkfun shows that both pressure and >>>>>>>>> temperature are output by the sensor. However, it does not show any >>>>>>>>> external processing which would be needed to provide compensation. >>>>>>>>> <https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation. >>>>>>>>>
I blundered across this explanation of how temperature compensations >>>>>>>>> works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?" >>>>>>>>> <https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is >>>>>>>>> interesting reading.
Calculating altitude with GPS seems to me to make more sense.
by how much and how much you care.
I?m more likely to note the temperature with all the caveat?s though more
likely in winter.
Roger Merriman
GPS altitude calculation should be more accurate if it can read four >>>>>> satellites.
********************************
Is GPS Accurate for Altitude?
Private Pilot
Made Easy
There is no such thing as a ?perfect? system, and GPS is no exception. >>>>>> When it works, it is highly accurate. In fact, there are currently >>>>>> plans to eventually replace conventional aviation navigation aids with >>>>>> GPS (GBAS) landing systems.
However, GPS altitude can be affected by the following: ?
Ionospheric errors ? The Earth is surrounded by layers of a dense
atmosphere that change in size and thickness depending on solar
activity and the time of day. This can cause minor altitude errors. >>>>>> Clock errors ? GPS clocks are phenomenally However, even a
minuscule disruption to their timing can cause errors. This doesn?t >>>>>> happen often, and GPS receivers normally discard a timing signal they >>>>>> recognize as erroneous.
Rounding errors ? Generally, these errors are small, but in an
aircraft, precision matters.
Satellite signal loss ? Like any piece of electrical equipment,
Satellites do sometimes stop working or are rebooted. For a GPS to >>>>>> provide accurate altitude readings, it needs multiple satellites,
normally four. If the fourth drops out at a critical time, this could >>>>>> cause issues.
https://pilotinstitute.com/altimeter-vs-gps-altitude/
*********************************
I understand that using four satellites, time errors can be
compensated, and four satellites are required for altitude
calculations anyway. It seems to me that the biggest problem with GPS >>>>>> altitude is possible loss of satellite reception, which is a serious >>>>>> issue for airplanes, but not such a big deal for land and sea
operations. Why Garmin and other land based GPS systems don't use GPS >>>>>> altitude is a mystery to me.
all have barometric sensors for improved accuracy, I?m assuming that while
GPS Altitude is indeed more accurate flying or sailing, this isn?t the same
cycling with sky cover and undulating land.
Ie clearly must be some engineering reason to do so, most likely the above.
Roger Merriman
I don't pay any attention to altitude on my rides, although it is
recorded on my Garmin computer. There are 30/40 foot variations in
maximum altitude when I compare identical rides, so whatever method
the computer uses is worthless.
I tended to ride in the early morning before going to work and so used
a simple - count the revolutions - speedometer to measurer speed and
distance and simply calculate the average speed for the morning's
ride. The fact that I got up a 1 mile long hill a bit faster, or
slower, was (to me) ]meaningless, it was the total time for the
entire ride divided by the miles traveled.
My Garmin computer counts the wheel revolutions to get speed and
distance, although it will use GPS if there is no wheel sensor or if
it fails. The computer also uses GPS to set the wheel circumference.
Total distance and average speed is also what I consider the most
significant data. Strava collects individual segment times so riders
can compare themselves with other riders, but I think that's silly.
Unless a person is among the best professional bike racers, there's
always going to be someone who is faster. It's just a matter of
picking who you're going to race against. Pick slower competitors and
you will win, pick faster competitors and you will lose. I only race
against myself.
ride always seems to end up averaging 11/12mph be that a chill in the woods >and maybe a ice cream or thrash along some of the farm tracks, all seems to >well average out.
But segments can tell a quite different story clearly lots of variables,
wet soggy gravel ie mud makes for slow going vs mid summer dust!
Roger Merriman
On 8/11/2024 2:36 PM, Roger Merriman wrote:
Average speed is personally one of the least useful metrics, as a gravel
ride always seems to end up averaging 11/12mph be that a chill in the woods >> and maybe a ice cream or thrash along some of the farm tracks, all seems to >> well average out.
An important point is that for flat bike trails, power required
increases roughly as the cube of speed. If a person is "in training"
(for what?) and they increase their personal power by 10% - which takes
some intense training - they'd only see something like a 3% increase in speed. That's a difference that's easily lost in the noise. All this
makes average speed on the flat a pretty lousy method of trying to
detect personal improvement.
On steep climbs, speed is much closer to directly proportional to power. Measuring one's hill climbing speed would be a better gauge of personal
power gains, training improvements, etc.
On Sat, 10 Aug 2024 14:12:12 -0400,
Frank Krygowski <frkrygow@sbcglobal.net> wrote:
On 8/10/2024 12:21 PM, Jeff Liebermann wrote:
GPS is far more accurate measuring 2D surface distances than
3D measuring altitude. "Grade, Elevation, and GPS Accuracy
FAQ"
<https://support.ridewithgps.com/hc/en-us/articles/4419010957467-Grade-Elevation-and-GPS-Accuracy-FAQ>
Garmin rates their GPS elevation accuracy at +/-400 ft and
their barometric elevation accuracy at +/-50 ft.
If anyone wants me to explain why in excruciating detail if
anyone is interested. The short version is that GPS works by
measuring the Doppler shifts produced by multiple satellites
across the sky. The motion of the satellite has to be mostly
toward or away from the GPS receiver. For altitude, that
happens best when the satellites are near the horizon. A
satellite directly overhead does not move toward or away from
the GPS receiver and is therefore useless for computing
altitude. Since the horizon tends to be cluttered with
mountains, trees, buildings, reflections etc, the signals from
the best positioned satellites can't be used. Just to make
things difficult, the better GPS antennas are designed to
suppress ground reflections which makes using low elevation
satellites even more difficult to use.
Yep, and nice explanation.
IIRC, Jobst explained that with some trigonometric detail many
years ago.
And it's all irrelevant for Florida bike paths.
LOL Reminds me of a tandem rally in Sebring a few years ago. At
one point we rode with a couple from Ft. Lauderdale and had a hard
time keeping straight faces when they complained about the hills.
On Sun, 11 Aug 2024 16:09:37 -0400, Catrike Ryder
<Soloman@old.bikers.org> wrote:
On Sun, 11 Aug 2024 17:46:37 -0000 (UTC), Ted Heise <theise@panix.com> >>wrote:
On Sat, 10 Aug 2024 14:12:12 -0400,
Frank Krygowski <frkrygow@sbcglobal.net> wrote:
On 8/10/2024 12:21 PM, Jeff Liebermann wrote:
GPS is far more accurate measuring 2D surface distances than
3D measuring altitude. "Grade, Elevation, and GPS Accuracy
FAQ"
<https://support.ridewithgps.com/hc/en-us/articles/4419010957467-Grade-Elevation-and-GPS-Accuracy-FAQ>
Garmin rates their GPS elevation accuracy at +/-400 ft and
their barometric elevation accuracy at +/-50 ft.
If anyone wants me to explain why in excruciating detail if
anyone is interested. The short version is that GPS works by
measuring the Doppler shifts produced by multiple satellites
across the sky. The motion of the satellite has to be mostly
toward or away from the GPS receiver. For altitude, that
happens best when the satellites are near the horizon. A
satellite directly overhead does not move toward or away from
the GPS receiver and is therefore useless for computing
altitude. Since the horizon tends to be cluttered with
mountains, trees, buildings, reflections etc, the signals from
the best positioned satellites can't be used. Just to make
things difficult, the better GPS antennas are designed to
suppress ground reflections which makes using low elevation
satellites even more difficult to use.
Yep, and nice explanation.
IIRC, Jobst explained that with some trigonometric detail many
years ago.
And it's all irrelevant for Florida bike paths.
LOL Reminds me of a tandem rally in Sebring a few years ago. At
one point we rode with a couple from Ft. Lauderdale and had a hard
time keeping straight faces when they complained about the hills.
I don't ever ride with anyone, but I do hear from northerners at rest
stops complaining about the heat and humidity. I'm going to ride
Tuesday morning and I expect to see 90 degrees and 80+ humidity.
Having have ridden in tropical countries for much of my life the
solution is to start your ride at sun up and finish by 09:00 or maybe
a bit later.
Here it is the rainy season - the coolest time of the year - and at
the moment, 07:24, the temperature is 28 degrees C (82 F) and it is
expected to be 31 degrees (87 F) by noon.
On Mon, 12 Aug 2024 07:43:11 +0700, John B. <slocombjb@gmail.com>
wrote:
On Sun, 11 Aug 2024 16:09:37 -0400, Catrike Ryder
<Soloman@old.bikers.org> wrote:
On Sun, 11 Aug 2024 17:46:37 -0000 (UTC), Ted Heise <theise@panix.com>
wrote:
On Sat, 10 Aug 2024 14:12:12 -0400,
Frank Krygowski <frkrygow@sbcglobal.net> wrote:
On 8/10/2024 12:21 PM, Jeff Liebermann wrote:
GPS is far more accurate measuring 2D surface distances than
3D measuring altitude. "Grade, Elevation, and GPS Accuracy
FAQ"
<https://support.ridewithgps.com/hc/en-us/articles/4419010957467-Grade-Elevation-and-GPS-Accuracy-FAQ>
Garmin rates their GPS elevation accuracy at +/-400 ft and
their barometric elevation accuracy at +/-50 ft.
If anyone wants me to explain why in excruciating detail if
anyone is interested. The short version is that GPS works by
measuring the Doppler shifts produced by multiple satellites
across the sky. The motion of the satellite has to be mostly
toward or away from the GPS receiver. For altitude, that
happens best when the satellites are near the horizon. A
satellite directly overhead does not move toward or away from
the GPS receiver and is therefore useless for computing
altitude. Since the horizon tends to be cluttered with
mountains, trees, buildings, reflections etc, the signals from
the best positioned satellites can't be used. Just to make
things difficult, the better GPS antennas are designed to
suppress ground reflections which makes using low elevation
satellites even more difficult to use.
Yep, and nice explanation.
IIRC, Jobst explained that with some trigonometric detail many
years ago.
And it's all irrelevant for Florida bike paths.
LOL Reminds me of a tandem rally in Sebring a few years ago. At
one point we rode with a couple from Ft. Lauderdale and had a hard
time keeping straight faces when they complained about the hills.
I don't ever ride with anyone, but I do hear from northerners at rest
stops complaining about the heat and humidity. I'm going to ride
Tuesday morning and I expect to see 90 degrees and 80+ humidity.
Having have ridden in tropical countries for much of my life the
solution is to start your ride at sun up and finish by 09:00 or maybe
a bit later.
Here it is the rainy season - the coolest time of the year - and at
the moment, 07:24, the temperature is 28 degrees C (82 F) and it is
expected to be 31 degrees (87 F) by noon.
I will start very early, but my rides last at least four hours, maybe
longer, so I'm going to experience 90 degrees or more. I'll be ok as
long as I keep moving and generating a breeze and only stop in the
shade. I'm a prolific sweater and I'll be taking six 24 oz bottles of Gatorade and/or water and there'll be places I can stop and fill them
up.
On Sat, 10 Aug 2024 14:12:12 -0400,
Frank Krygowski <frkrygow@sbcglobal.net> wrote:
On 8/10/2024 12:21 PM, Jeff Liebermann wrote:
GPS is far more accurate measuring 2D surface distances than
3D measuring altitude. "Grade, Elevation, and GPS Accuracy
FAQ"
<https://support.ridewithgps.com/hc/en-us/articles/4419010957467-Grade-Elevation-and-GPS-Accuracy-FAQ>
Garmin rates their GPS elevation accuracy at +/-400 ft and
their barometric elevation accuracy at +/-50 ft.
If anyone wants me to explain why in excruciating detail if
anyone is interested. The short version is that GPS works by
measuring the Doppler shifts produced by multiple satellites
across the sky. The motion of the satellite has to be mostly
toward or away from the GPS receiver. For altitude, that
happens best when the satellites are near the horizon. A
satellite directly overhead does not move toward or away from
the GPS receiver and is therefore useless for computing
altitude. Since the horizon tends to be cluttered with
mountains, trees, buildings, reflections etc, the signals from
the best positioned satellites can't be used. Just to make
things difficult, the better GPS antennas are designed to
suppress ground reflections which makes using low elevation
satellites even more difficult to use.
Yep, and nice explanation.
IIRC, Jobst explained that with some trigonometric detail many
years ago.
And it's all irrelevant for Florida bike paths.
LOL Reminds me of a tandem rally in Sebring a few years ago. At
one point we rode with a couple from Ft. Lauderdale and had a hard
time keeping straight faces when they complained about the hills.
The short version is that GPS works by measuring the
Doppler shifts produced by multiple satellites across the sky. The
motion of the satellite has to be mostly toward or away from the GPS >receiver. For altitude, that happens best when the satellites are
near the horizon. A satellite directly overhead does not move toward
or away from the GPS receiver and is therefore useless for computing >altitude. Since the horizon tends to be cluttered with mountains,
trees, buildings, reflections etc, the signals from the best
positioned satellites can't be used. Just to make things difficult,
the better GPS antennas are designed to suppress ground reflections
which makes using low elevation satellites even more difficult to use.
On Thu, 08 Aug 2024 08:22:35 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:
On Thu, 08 Aug 2024 10:18:39 GMT, Roger Merriman <roger@sarlet.com>
wrote:
Jeff Liebermann <jeffl@cruzio.com> wrote:
On Wed, 07 Aug 2024 17:57:59 GMT, Tom Kunich <cyclintom@yahoo.com>
wrote:
The formula for change in altitude with air pressure in the lower
atmosphere (about to 35,000 feet) is:
Nope. From what's left of your formula, I'll assume you're trying to
calculate the air pressure at a given altitude. There is no *change*
in altitude involved. Looks like you lost all the Greek letter
symbols and formula symbols.
P=Pb[1
Where:
Pb
TM,b
LM,b
h
hb
R
g0
M
That unreadable mess should look something like these:
"Atmospheric Pressure Calculator"
<https://calculator.academy/atmospheric-pressure-calculator/>
"Air Pressure at Altitude Calculator"
<https://www.omnicalculator.com/physics/air-pressure-at-altitude>
Note that you need to know the barometric base pressure (Pb) at sea
level for such a calculation to work. It's NOT going to work if your
riding up or down a hill where the barometric pressure might change.
In fairness the 830 recalculates on start up every so often particularly if >>it?s a changed location or it may well do so every time but don?t watch it >>start up in general.
Roger Merriman
Garmin works in mysterious ways. Garmin's self calibration algorithm
is a bit stranger than one might expect. For example: ><https://forums.garmin.com/sports-fitness/cycling/f/edge-830/174850/elevation-auto-calibration>
"Every time I start to record an activity on my Edge 830 I get this
message "Elevation calibrated to location" and immediately the
elevation number goes up by +/-12m out of the blue with me standing
still in the same spot.
The problem is that the elevation shown right before I press the
record button (before the "auto-calibration) is more accurate than the
one modified."
"The value is coming from the saved location that is near your
starting point."
I seem to recall reading somewhere that Garmin recommends calibration >before starting on a ride. I'm too lazy to find where Garmin said
that.
However, that message is over 5 years old and the problem might have
been fixed long ago with a firmware update.
The barometric altimeter accuracy in the Garmin Edge 830 is specified
at +/-50 ft accuracy (which is better than the +/-400 ft accuracy for
the GPS). There's also a +/-10 ft error for reasons unknown: ><https://support.garmin.com/en-US/?faq=sFMkjQFdnZ99DcunfAue66>
"Elevation accuracy of +/-10 meters is for any given reading during an >activity, not the total elevation gain/loss at the end of an
activity."
Very mysterious methinks.
Just how do these garmin gizmos work? Back when I worked on airplanes
the Altimeter measured the altitude above the home field. During
preflight, before engine start, the altimeter was set to "zero" and
during that flight measured height above the location where it was
set.
I believe in more modern times one calls the "Tower" and they give you
the altitude above sea level corrected by current temperature.
Where does the Garmin gets it base altitude from or is "0" simply the altitude, and temperature, when/where you turn it on?
--
Cheers,
John B.
On Fri, 09 Aug 2024 08:14:59 +0700, John B. <slocombjb@gmail.com>
wrote:
On Thu, 08 Aug 2024 08:22:35 -0700, Jeff Liebermann <jeffl@cruzio.com> >wrote:
On Thu, 08 Aug 2024 10:18:39 GMT, Roger Merriman <roger@sarlet.com> >>wrote:
Jeff Liebermann <jeffl@cruzio.com> wrote:
On Wed, 07 Aug 2024 17:57:59 GMT, Tom Kunich <cyclintom@yahoo.com>
wrote:
The formula for change in altitude with air pressure in the lower
atmosphere (about to 35,000 feet) is:
Nope. From what's left of your formula, I'll assume you're trying to >>>> calculate the air pressure at a given altitude. There is no *change* >>>> in altitude involved. Looks like you lost all the Greek letter
symbols and formula symbols.
P=Pb[1
Where:
Pb
TM,b
LM,b
h
hb
R
g0
M
That unreadable mess should look something like these:
"Atmospheric Pressure Calculator"
<https://calculator.academy/atmospheric-pressure-calculator/>
"Air Pressure at Altitude Calculator"
<https://www.omnicalculator.com/physics/air-pressure-at-altitude>
Note that you need to know the barometric base pressure (Pb) at sea
level for such a calculation to work. It's NOT going to work if your >>>> riding up or down a hill where the barometric pressure might change.
In fairness the 830 recalculates on start up every so often particularly if
it?s a changed location or it may well do so every time but don?t watch it >>>start up in general.
Roger Merriman
Garmin works in mysterious ways. Garmin's self calibration algorithm
is a bit stranger than one might expect. For example: >><https://forums.garmin.com/sports-fitness/cycling/f/edge-830/174850/elevation-auto-calibration>
"Every time I start to record an activity on my Edge 830 I get this >>message "Elevation calibrated to location" and immediately the
elevation number goes up by +/-12m out of the blue with me standing
still in the same spot.
The problem is that the elevation shown right before I press the
record button (before the "auto-calibration) is more accurate than the >>one modified."
"The value is coming from the saved location that is near your
starting point."
I seem to recall reading somewhere that Garmin recommends calibration >>before starting on a ride. I'm too lazy to find where Garmin said
that.
However, that message is over 5 years old and the problem might have
been fixed long ago with a firmware update.
The barometric altimeter accuracy in the Garmin Edge 830 is specified
at +/-50 ft accuracy (which is better than the +/-400 ft accuracy for
the GPS). There's also a +/-10 ft error for reasons unknown: >><https://support.garmin.com/en-US/?faq=sFMkjQFdnZ99DcunfAue66>
"Elevation accuracy of +/-10 meters is for any given reading during an >>activity, not the total elevation gain/loss at the end of an
activity."
Very mysterious methinks.
Just how do these garmin gizmos work? Back when I worked on airplanes
the Altimeter measured the altitude above the home field. During
preflight, before engine start, the altimeter was set to "zero" and
during that flight measured height above the location where it was
set.
I believe in more modern times one calls the "Tower" and they give you
the altitude above sea level corrected by current temperature.
Where does the Garmin gets it base altitude from or is "0" simply the >altitude, and temperature, when/where you turn it on?
A barometric altimeter works in a similar, but not identical way. For Garmin, you calibrate the altimeter from a known altitude location
from a designated reference. If your starting location is known to be
100 ft AMSL (above mean sea level), you set your Garmin for 100ft and
you're done. If you don't have an accurate map, using the GPS
altitude, averaged over a long period will suffice, but you need to
enter the datum used to define zero altitude used by the GPS. Notice
that you don't enter the barometric pressure to make this work. For
the Garmin 830, in manual mode, it's simply set and ride: <https://www8.garmin.com/manuals/webhelp/edge830/EN-US/GUID-1833C7CC-667E-48C7-B7D2-7A6041470478.html>
On later devices, Garmin uses the GPS altitude and DEM (digital
elevation model) to calibrate the barometer. This is for the Garmin Forerunner 965 watch: <https://www8.garmin.com/manuals/webhelp/GUID-0221611A-992D-495E-8DED-1DD448F7A066/EN-US/GUID-BC734846-01A7-4F33-86D4-DFBDBC06CDB4.html>
Again, notice that barometric pressure is not involved in establishing
a reference altitude.
Garmin also has an "auto cal" mode, which does all this automagically.
I couldn't find an explanation on how it works from Garmin. My
guess(tm) is that it uses the nearest GPS reference available where
the bicycle was not moving and the DOP (dilution of precision) is sufficiently low for the GPS altitude to be considered accurate. <https://en.wikipedia.org/wiki/Dilution_of_precision_(navigation)>
Again, notice that barometric pressure is not involved in establishing
a reference altitude.
Once a reference altitude is established, the barometric pressure
becomes involved. The math is easy enough:
"Atmospheric Pressure Calculator" <https://calculator.academy/atmospheric-pressure-calculator/>
"Air Pressure at Altitude Calculator" <https://www.omnicalculator.com/physics/air-pressure-at-altitude>
For faster response, Garmin might use a lookup table to convert air
pressure to altitude.
However, barometric pressure change with weather, location and
environment. The MEMS pressure sensor might also drift. Therefore,
the altitude must be recalibrated occasionally. My guess(tm) is that
Garmin uses the nearest known GPS location, with the lowest DOP, to
establish a new reference. If the new reference altitude is not quite perfect, the rider sees a "glitch" or discontinuity in the elevation
profile graph when the reference is reset. Garmin probably tries to
"smooth" this transition, making the graph look more reasonable.
I was wondering why Garmin elevation accuracy specification for the
Edge 830 was +/-400 ft. GPS elevation accuracy should be about +/-120
ft for most GPS's. Some possible causes are:
1. The EDGE 830 was turned off at night and not given sufficient time
to download a few days worth of ephemeris data. Garmin advised to put
the GPS somewhere with a good view of the sky and let it download for
about 15(?) mins.
2. The GPS antenna on the 830 is probably tiny. That will reduce
signal strength and therefore accuracy.
3. The Sony GPS receiver on the 830 uses GPS and *EITHER* Glonass or Galileo. It really should be using all three to see more satellites.
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
On Fri Aug 9 08:14:59 2024 John B. wrote:
Where does the Garmin gets it base altitude from or is "0" simply the
altitude, and temperature, when/where you turn it on?
John, it wasn't set to zero but to the altitude of the field which was
known though survey's. A pressure detector is nothing more than a
diaphram with a known pressure on one side. The diaphram flexes with a
change in pressure while at the same time corrected for temperature
which in our day was a rather complicated bimetalic arm that would flex
with a change in temperature and use a change in tghe length of the
pressure detector arm olength to correct. This sounds very complicated
but remember that Swiss watchmakers originally mader all of those gears
in a Swiss watch with jewles files and a lot of patience.
On 8/10/2024 3:39 AM, Catrike Ryder wrote:
On Fri, 09 Aug 2024 17:36:48 -0700, Jeff Liebermann <jeffl@cruzio.com> wrote:
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com>
wrote:
The basic system sounds much like my old airplane altimeter. But how
is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin,
has a built in temperature sensor and compensates internally.
<https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C
temperature accuracy. However, I can't tell if the pressure numbers
the sensor produces are pre-compensated internally in the sensor, or
if the pressure is calculated externally with a connected micro
controller. In other words, I don't know how Garmin does temperature
compensation.
The supplied code from Sparkfun shows that both pressure and
temperature are output by the sensor. However, it does not show any
external processing which would be needed to provide compensation.
<https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation.
I blundered across this explanation of how temperature compensations
works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?"
<https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is
interesting reading.
Calculating altitude with GPS seems to me to make more sense.
But not until crystal clocks, computing power and a
satellite network came together. See also ocean navigation
which was adequate before GPS but arguably better with it.
In our brave new world there aren't redundant systems and
one wonders about an EMP event for a Navy with no sextants...
--
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971
On Fri Aug 9 10:44:09 2024 Jeff Liebermann wrote:
On the right side of a Garmin 830 is a perhaps 2 mm hole, I assume this
goes into a weather tight chamber where rathger than a diaphram detector
it uses a silicon sheet suspended over the detrector which flexes with pressure. It is an analog device whick probably limits its accuracy But climbing a 10% slope it changes every one or two pedal strokes. by one
or two feet. So it is pretty sensitive.
at sea level,
pressure changes about 0.03 hPa/inch.
On Fri, 08 Nov 2024 19:23:25 GMT, cyclintom <cyclintom@yahoo.com>
wrote:
Remember that ALL metals expand when heated but they expand...
Almost everything expands when heated. That includes all subject
material which greatly expands during a heated debate.
However, Invar (a nickel-iron alloy) doesn't expand when heated:
"Some Alloys Don't Change Size When Heated. We Now Know Why." <https://www.caltech.edu/about/news/some-alloys-dont-change-size-when-heated-we-now-know-why>
"Thermal expansion occurs because a material's atoms vibrate more as
its temperature increases. The more its atoms vibrate, the more they
push away from their neighboring atoms. As the space between the atoms increases, the density of the material decreases and its overall size increases."
I wonder if vibranium or reverbium expand when heated? <https://en.wikipedia.org/wiki/Vibranium>
I also suspect that metal coins shrink in my pocket because when I
spend the coins, they always seem to buy less than when I previously
spent them.
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
On 11/8/2024 3:59 PM, Zen Cycle wrote:
New meds?
That's a possibility. _Something_ has certainly happened to Tom in the
last few days!
--
- Frank Krygowski
On 11/8/2024 4:41 PM, Frank Krygowski wrote:
On 11/8/2024 3:59 PM, Zen Cycle wrote:
New meds?
That's a possibility. _Something_ has certainly happened to Tom in the
last few days!
I'm thinking it was an endorphin rush from the election results, maybe
he's finally coming down.
--
Add xx to reply
On Sun, 11 Aug 2024 17:46:37 -0000 (UTC), Ted Heise <theise@panix.com>
wrote:
On Sat, 10 Aug 2024 14:12:12 -0400,
Frank Krygowski <frkrygow@sbcglobal.net> wrote:
On 8/10/2024 12:21 PM, Jeff Liebermann wrote:
GPS is far more accurate measuring 2D surface distances than
3D measuring altitude. "Grade, Elevation, and GPS Accuracy
FAQ"
<https://support.ridewithgps.com/hc/en-us/articles/4419010957467-Grade-Elevation-and-GPS-Accuracy-FAQ>
Garmin rates their GPS elevation accuracy at +/-400 ft and
their barometric elevation accuracy at +/-50 ft.
If anyone wants me to explain why in excruciating detail if
anyone is interested. The short version is that GPS works by
measuring the Doppler shifts produced by multiple satellites
across the sky. The motion of the satellite has to be mostly
toward or away from the GPS receiver. For altitude, that
happens best when the satellites are near the horizon. A
satellite directly overhead does not move toward or away from
the GPS receiver and is therefore useless for computing
altitude. Since the horizon tends to be cluttered with
mountains, trees, buildings, reflections etc, the signals from
the best positioned satellites can't be used. Just to make
things difficult, the better GPS antennas are designed to
suppress ground reflections which makes using low elevation
satellites even more difficult to use.
Yep, and nice explanation.
Thanks. I just realized that it would take me several days to explain exactly how GPS/GNSS elevation accuracy works for all the various
generations of satellites that are buzzing around overhead. However,
if I just explain the stuff that is relevant to the various Garmin
products and only deals with elevation (and not with position), I
think I can throw something together in an hour or two. Will that
level of detail be sufficiently excruciating?
Meanwhile, this looks interesting:
"Compared - Elevation Accuracy of GPS Watches" (March 24, 2023) <https://geeksonfeet.com/blog/gpswatch-elevations/>
Yes, I know it's for running and not cycling, but that's the best I
could do for now.
IIRC, Jobst explained that with some trigonometric detail many
years ago.
And it's all irrelevant for Florida bike paths.
LOL Reminds me of a tandem rally in Sebring a few years ago. At
one point we rode with a couple from Ft. Lauderdale and had a hard
time keeping straight faces when they complained about the hills.
Nice. I also could use a good laugh today. What level of elevation
(not position) accuracy do you consider adequate when moving and when stopped?
The commonly used SRTM2 (shuttle radar topography mission v2)
elevation maps show RMS (root mean square) errors of 3 to 5 meters
depending on terrain and land use. Finding the ground through an
overhead tree canopy can introduce some rather interesting errors[1]: "Accuracy Assessment of Elevation Data" <https://www.usgs.gov/special-topics/significant-topographic-changes-in-the-united-states/science/accuracy-assessment>
LiDAR is more accurate, but currently only for specific and limited
areas of interest:
"California LiDAR Status Map" <https://www.arcgis.com/apps/View/index.html?appid=9204adf2fd1546379b845d163ef2544a>
Eventually, we'll have downloadable LiDAR maps where the elevation or altitude can be determined by a map lookup using the more accurate GPS position.
[1] The early SRTM maps had some unusual topographic details. For
example, when the RADAR could not produce a reasonable altitude, it
would produce a zero altitude data point. When in doubt, zero should suffice. When applications software based on the SRTM maps became
commonly available, the landscape was dotted with numerous large holes extending to the center of the earth.
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
On Fri, 09 Aug 2024 17:36:48 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com>
wrote:
The basic system sounds much like my old airplane altimeter. But how
is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin,
has a built in temperature sensor and compensates internally. ><https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C >temperature accuracy. However, I can't tell if the pressure numbers
the sensor produces are pre-compensated internally in the sensor, or
if the pressure is calculated externally with a connected micro
controller. In other words, I don't know how Garmin does temperature >compensation.
The supplied code from Sparkfun shows that both pressure and
temperature are output by the sensor. However, it does not show any >external processing which would be needed to provide compensation. ><https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation.
I blundered across this explanation of how temperature compensations
works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?" ><https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is >interesting reading.
Calculating altitude with GPS seems to me to make more sense.
On Sat, 10 Aug 2024 04:39:21 -0400, Catrike Ryder
<Soloman@old.bikers.org> wrote:
On Fri, 09 Aug 2024 17:36:48 -0700, Jeff Liebermann <jeffl@cruzio.com> >wrote:
On Sat, 10 Aug 2024 07:02:48 +0700, John B. <slocombjb@gmail.com>
wrote:
The basic system sounds much like my old airplane altimeter. But how
is atmospheric pressure due to temperature handled?
The MEMS barometric sensor, which I guessed was being used by Garmin,
has a built in temperature sensor and compensates internally. >><https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
The data sheet claims "embedded temperature compensation" and +/-1.5C >>temperature accuracy. However, I can't tell if the pressure numbers
the sensor produces are pre-compensated internally in the sensor, or
if the pressure is calculated externally with a connected micro >>controller. In other words, I don't know how Garmin does temperature >>compensation.
The supplied code from Sparkfun shows that both pressure and
temperature are output by the sensor. However, it does not show any >>external processing which would be needed to provide compensation. >><https://learn.sparkfun.com/tutorials/sparkfun-absolute-digital-barometer---lps28dfw-qwiic-hookup-guide#lps28dfw-arduino-library>
Once again, I don't know how Garmin does temperature compensation.
I blundered across this explanation of how temperature compensations >>works in an aircraft altimeter:
"What does setting an altimeter actually do to the altitude?" >><https://aviation.stackexchange.com/questions/87848/what-does-setting-an-altimeter-actually-do-to-the-altitude>
I don't really know if that helps answer your question but it is >>interesting reading.
Calculating altitude with GPS seems to me to make more sense.
GPS is far more accurate measuring 2D surface distances than 3D
measuring altitude.
"Grade, Elevation, and GPS Accuracy FAQ" <https://support.ridewithgps.com/hc/en-us/articles/4419010957467-Grade-Elevation-and-GPS-Accuracy-FAQ>
Garmin rates their GPS elevation accuracy at +/-400 ft and their
barometric elevation accuracy at +/-50 ft.
If anyone wants me to explain why in excruciating detail if anyone is interested. The short version is that GPS works by measuring the
Doppler shifts produced by multiple satellites across the sky. The
motion of the satellite has to be mostly toward or away from the GPS receiver. For altitude, that happens best when the satellites are
near the horizon. A satellite directly overhead does not move toward
or away from the GPS receiver and is therefore useless for computing altitude. Since the horizon tends to be cluttered with mountains,
trees, buildings, reflections etc, the signals from the best
positioned satellites can't be used. Just to make things difficult,
the better GPS antennas are designed to suppress ground reflections
which makes using low elevation satellites even more difficult to use.
If you want accurate elevations, the antenna needs to be larger and
more complex than what's found in Garmin products. Something like
these:
<https://www.google.com/search?q=gps+choke+ring+antenna&tbm=isch> <https://en.wikipedia.org/wiki/Choke_ring_antenna>
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
On Mon, 09 Sep 2024 23:18:56 GMT, cyclintom wrote:
You're still replying to a month old article.
On Fri Aug 9 10:44:09 2024 Jeff Liebermann wrote:
On the right side of a Garmin 830 is a perhaps 2 mm hole, I assume this goes into a weather tight chamber where rathger than a diaphram detector
it uses a silicon sheet suspended over the detrector which flexes with pressure. It is an analog device whick probably limits its accuracy But climbing a 10% slope it changes every one or two pedal strokes. by one
or two feet. So it is pretty sensitive.
Mostly wrong. The MEMS sensor can be piezo-resistive or capacitive. Both are analog, are amplified on the MEMS device, and are digitized on the
MEMS device to a common communications bus, such as I2C. I haven't found autopsy photos for the Edge 830 so I'm not sure what the device might be.
My best guess(tm) is this LPS28DFW piezo-resistive device: <https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
Is an absolute pressure accuracy of 0.5 hPa in a 24 bit word sufficient accuracy?
If the pressure changes every "one or two feet" (which it doesn't), do you have something against using averaging to smooth the data? At sea level, pressure changes about 0.03 hPa/inch. You might see the change, but it
will be buried under the 0.32 Pa noise level.
I seem to remember posting most of this information previously for your benefit.
Posted with Pan for Linux 0.155
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
Tell us all here what that is supposed to mean?
Not expanding is nothing more than a different rate of expansion.
Without different rates of expansion you CANNOT correct
for temperature variations
but again you have to pretend to be the expert.
What kind of dumb shit tries to find something that he doesn't
even understand to think he is correcting my statement?
Tell us again how altitude is measure with a GPS signzal, that was a good one as well.
On Tue Sep 10 03:33:23 2024 Jeff Liebermann wrote:
On Mon, 09 Sep 2024 23:18:56 GMT, cyclintom wrote:
You're still replying to a month old article.
On Fri Aug 9 10:44:09 2024 Jeff Liebermann wrote:
On the right side of a Garmin 830 is a perhaps 2 mm hole, I assume this
goes into a weather tight chamber where rathger than a diaphram detector >> > it uses a silicon sheet suspended over the detrector which flexes with
pressure. It is an analog device whick probably limits its accuracy But
climbing a 10% slope it changes every one or two pedal strokes. by one
or two feet. So it is pretty sensitive.
Mostly wrong. The MEMS sensor can be piezo-resistive or capacitive. Both >> are analog, are amplified on the MEMS device, and are digitized on the
MEMS device to a common communications bus, such as I2C. I haven't found
autopsy photos for the Edge 830 so I'm not sure what the device might be.
My best guess(tm) is this LPS28DFW piezo-resistive device:
<https://www.st.com/resource/en/datasheet/lps28dfw.pdf>
Is an absolute pressure accuracy of 0.5 hPa in a 24 bit word sufficient
accuracy?
If the pressure changes every "one or two feet" (which it doesn't), do you >> have something against using averaging to smooth the data? At sea level,
pressure changes about 0.03 hPa/inch. You might see the change, but it
will be buried under the 0.32 Pa noise level.
I seem to remember posting most of this information previously for your
benefit.
Posted with Pan for Linux 0.155
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
Piezo resistive?
Why are you talking continually about things you don't know about?
You still haven't told us how you think a TV90 ground faulr detector works.
Shouldn't you be out riding a mile on a junk bike in order to prove you're a cyclist and deserve the right to tell us all how to ride?
On Fri Nov 8 16:48:21 2024 Zen Cycle wrote:
On 11/8/2024 4:41 PM, Frank Krygowski wrote:
On 11/8/2024 3:59 PM, Zen Cycle wrote:
New meds?
That's a possibility. _Something_ has certainly happened to Tom in the
last few days!
I'm thinking it was an endorphin rush from the election results, maybe
he's finally coming down.
--
Add xx to reply
Again posting during business hours. Tell us what business you're really in, Babysitting? Pretending to us that you are an EE?
On Fri Nov 8 15:59:17 2024 Zen Cycle wrote:rotation against another.
On 11/8/2024 2:23 PM, cyclintom wrote:
On Sun Aug 11 13:26:43 2024 Frank Krygowski wrote:
On 8/10/2024 8:38 PM, Jeff Liebermann wrote:
I just opened up the wall mounted aneroid barometer here in my study, an >>>> antique I inherited. It's an extremely simple lever mechanism, no gears >>>> involved. The capsule pushes up or down on a long thin lever arm. The
As I understand it, all aviation barometric altimeters are temperature >>>>> compensated. I would think the aviation temperature compensation for >>>>> air density method is somewhat similar to a marine barometer:
<https://www.faa.gov/air_traffic/publications/atpubs/aip_html/part2_enr_section_1.8.html>
I couldn't find anything that shows how the various gears work and
where the bi-metallic temperature compensator is located (because of >>>>> numerous interruptions today).
vertical motion of the lever's end is converted to a horizontal motion >>>> of a tall thin post, which anchors the end of the smallest roller-style >>>> chain I've ever seen, maybe 0.050" pitch. That wraps around the needle's >>>> pivot shaft. Here's a photo:
https://www.flickr.com/photos/16972296@N08/53916400376/in/dateposted-public/
(Sorry, the "tall thin post" is in shadow.)
The left end of the lever system is not a pivot point, but instead is a >>>> rather wide brass stamping. I'd think that part could be made bimetallic >>>> to provide temperature compensation.
--
- Frank Krygowski
Remember that ALL metals expand when heated but they expand at different rates so the mechanism has to correct the expansion of one metal against the expansion of the other for compensation so there has to be a mechanism that puts one point of
compensation.
I wish that Liebermann would stop trying to be an expert at things he doesn't understand. He said that my way of using a pulse width to measure a line length so that you can zero in on the reflection point is wrong
Yes, it was wrong. You claimed you were using PWM, but you were
describing TDR, and describing it incorrectly. And no, TDR does not use
PWM to manipulate the pulse width.
but offered NO alternative
Yes, he and I both did, explaining the _correct_ way to use TDR without
a specific TDR tester.
and then just the other day showed a TV90 and pretended that to be the alternative.
It's a TDR test set. It's what we've been stating you were doing all
along, not PWM. IT says so right on the page
https://www.atecorp.com/products/tektronix/tv90
He has NO idea of how a TV90 works
He described TDR rather well, you're just too stupid to understand it.
you on the OTH didn't even know what TDR actually meant until it was
explained to you (you called it "time delay reflection", lol
https://groups.google.com/g/rec.bicycles.tech/c/f_tByXh5jXo/m/CNLtZacUCAAJ) >>
which just happens to be a sophisticated copy of my way that is used to find cable faults in underground lines. Tektronics makes the TV100 which is a further sophistication.
And you won't find PWM anywhere in any description of TDR.
He did the same thing when I wrote the formula of how altitude via air pressure is calculated. He writes the same thing and claims that I am wrong because it doesn't include compensation. If sea level pressure is unchanged there needs be no
once I used Campy 12 speed and Shimano Di2) because it is good enough for the way in which I ride. Your 7 speeds are fine for you. We agree to disagree about helmets and bike lanes. As long as you do not oppose people's choices in your state, that's good
lol - the barometeric pressure at sea level changes by the hour,
sometimes faster, so yes, you need compensation.
And you can't be in two places at one time. Wait, Lieberrmann can, just ask him.
The world is simulaneously complicated and simple. The deeper you look the more complicated it becomes but for most things a very simple observation is all you need. You are happy with your steel bike. I prefer a more complex bike. I use 10 speed (
May you live to a healthy old age in a time of the party of Lincoln.
New meds?
--
Add xx to reply
Again I see that you're posting like crazy during business hours. You are a thief and nothing less. And a company that employes people like you and your boss cannot compete in the new world order of efficiency
On 11/9/2024 10:44 AM, cyclintom wrote:
On Fri Nov 8 16:48:21 2024 Zen Cycle wrote:
On 11/8/2024 4:41 PM, Frank Krygowski wrote:
On 11/8/2024 3:59 PM, Zen Cycle wrote:
New meds?
That's a possibility. _Something_ has certainly happened to Tom in the >>>> last few days!
I'm thinking it was an endorphin rush from the election results, maybe
he's finally coming down.
--
Add xx to reply
Again posting during business hours. Tell us what business you're really
in, Babysitting? Pretending to us that you are an EE?
Tommy tommy tommy...
First off, I'm 3 hours ahead of you. I posted that at 4:48 PM my time.
2nd - I don't have set hours. Engineering staff in the vast majority of high-tech companies aren't told when they need to be there, for how
long, or how late they need to stay. I haven't had to worry about that
since I was a bench technician punching a time clock in the 1980s. It's
not uncommon for me - or anyone of the engineering staff here - to take
off in the afternoon or come in later in the morning becasue they had an errand to run.
This is how I know you were never more than a bench technician. If you
had any _real_ engineering experience, you'd know the term "working
hours" for engineering staff is nebulous at best. Hell, your "career" is
in the backyard of companies that pioneered the "work-life balance"
ethos, and you claim engineering staff are locked into rigid office hours?
3rd, I spent most of friday writing a rationale to defend suggested
changes to an ANSI Hazardous Location Standard, for a technical working
group I'm a member of. I finished it a little early. I could have stayed
home to do or maybe finished it up this weekend if I wanted to. It's a luxury/perk I have as the most senior individual in my department and
the title of "principle engineer".
And a company that employes people like you and your boss cannot compete in the new world order of efficiency
And once again, he who would be Jobst and ian't, comments. Now that Trump is in office, we will actuLLY have job growth and not the Frank type of Democrat lies about it. That means people won't be seeking college degrees in the sort of numbers that willsupport Youngstown.
Zen Cycle <funkmaster@hotmail.com> wrote:
On 11/9/2024 10:44 AM, cyclintom wrote:My wife who had been a IT manager/account’s definitely worked all sorts of hours, occasionally over the weekend with pizza/beer delivery paid for by
On Fri Nov 8 16:48:21 2024 Zen Cycle wrote:
On 11/8/2024 4:41 PM, Frank Krygowski wrote:
On 11/8/2024 3:59 PM, Zen Cycle wrote:
New meds?
That's a possibility. _Something_ has certainly happened to Tom in the >>>>> last few days!
I'm thinking it was an endorphin rush from the election results, maybe >>>> he's finally coming down.
--
Add xx to reply
Again posting during business hours. Tell us what business you're really >>> in, Babysitting? Pretending to us that you are an EE?
Tommy tommy tommy...
First off, I'm 3 hours ahead of you. I posted that at 4:48 PM my time.
2nd - I don't have set hours. Engineering staff in the vast majority of
high-tech companies aren't told when they need to be there, for how
long, or how late they need to stay. I haven't had to worry about that
since I was a bench technician punching a time clock in the 1980s. It's
not uncommon for me - or anyone of the engineering staff here - to take
off in the afternoon or come in later in the morning becasue they had an
errand to run.
This is how I know you were never more than a bench technician. If you
had any _real_ engineering experience, you'd know the term "working
hours" for engineering staff is nebulous at best. Hell, your "career" is
in the backyard of companies that pioneered the "work-life balance"
ethos, and you claim engineering staff are locked into rigid office hours? >>
3rd, I spent most of friday writing a rationale to defend suggested
changes to an ANSI Hazardous Location Standard, for a technical working
group I'm a member of. I finished it a little early. I could have stayed
home to do or maybe finished it up this weekend if I wanted to. It's a
luxury/perk I have as the most senior individual in my department and
the title of "principle engineer".
her work, and likewise sorted out problems when we were away in Australia,
so occasionally going home “early” or coming in late so not a problem!
Roger Merriman
On Sat, 09 Nov 2024 15:40:07 GMT, cyclintom <cyclintom@yahoo.com>
wrote:
And a company that employes people like you and your boss cannot compete in the new world order of efficiency
Working with you would not have been an improvement:
05/27/2024
Message-ID: <xl65O.105327$EkJ4.11941@fx14.iad> https://rec.bicycles.tech.narkive.com/KYEeykBo/riding-after-heavy-manual-labor#postXX
(I need to update the post number)
"...if I weren't there the chief instruments for finding the cause of
AIDS would have never been obtained as early as it was. I had SIX
degreed engineers, 3 EE's and 3 IT programmers fail to be able to even
keep up with me and the investors in those companies lost their
investments." etc...
On 11/11/2024 2:42 PM, Jeff Liebermann wrote:
On Sat, 09 Nov 2024 15:40:07 GMT, cyclintom <cyclintom@yahoo.com>
wrote:
And a company that employes people like you and your boss cannot compete in the new world order of efficiency
Working with you would not have been an improvement:
05/27/2024
Message-ID: <xl65O.105327$EkJ4.11941@fx14.iad>
https://rec.bicycles.tech.narkive.com/KYEeykBo/riding-after-heavy-manual-labor#postXX
(I need to update the post number)
"...if I weren't there the chief instruments for finding the cause of
AIDS would have never been obtained as early as it was. I had SIX
degreed engineers, 3 EE's and 3 IT programmers fail to be able to even
keep up with me and the investors in those companies lost their
investments." etc...
I missed that one
Q: what were IT engineers doing working on medical electronics?
A: They weren't.
1) There wasn't any such thing as an IT programmer when tommy was
working on the PCR
b) There wouldn't have been anything for an IT programmer to do on a
medical instrument in 1984 since there were no ethernet communication
ports back then (oh, wait, did tommy invent the internet?!?!?!)
III) The cause of aids was discovered 4 years before tommy worked on
the PCR system.
IOW - just another tommy tall tale
On 8/10/2024 8:38 PM, Jeff Liebermann wrote:
As I understand it, all aviation barometric altimeters are temperature compensated. I would think the aviation temperature compensation forI just opened up the wall mounted aneroid barometer here in my study, an antique I inherited. It's an extremely simple lever mechanism, no gears involved. The capsule pushes up or down on a long thin lever arm. The vertical motion of the lever's end is converted to a horizontal motion
air density method is somewhat similar to a marine barometer: <https://www.faa.gov/air_traffic/publications/atpubs/aip_html/part2_enr_section_1.8.html>
I couldn't find anything that shows how the various gears work and
where the bi-metallic temperature compensator is located (because of numerous interruptions today).
of a tall thin post, which anchors the end of the smallest roller-style
chain I've ever seen, maybe 0.050" pitch. That wraps around the needle's pivot shaft. Here's a photo: https://www.flickr.com/photos/16972296@N08/53916400376/in/dateposted-public/
(Sorry, the "tall thin post" is in shadow.)
The left end of the lever system is not a pivot point, but instead is a rather wide brass stamping. I'd think that part could be made bimetallic
to provide temperature compensation.
--
- Frank Krygowski
On Sun Aug 11 13:26:43 2024 Frank Krygowski wrote:
On 8/10/2024 8:38 PM, Jeff Liebermann wrote:
I just opened up the wall mounted aneroid barometer here in my study, an
As I understand it, all aviation barometric altimeters are temperature
compensated. I would think the aviation temperature compensation for
air density method is somewhat similar to a marine barometer:
<https://www.faa.gov/air_traffic/publications/atpubs/aip_html/part2_enr_section_1.8.html>
I couldn't find anything that shows how the various gears work and
where the bi-metallic temperature compensator is located (because of
numerous interruptions today).
antique I inherited. It's an extremely simple lever mechanism, no gears
involved. The capsule pushes up or down on a long thin lever arm. The
vertical motion of the lever's end is converted to a horizontal motion
of a tall thin post, which anchors the end of the smallest roller-style
chain I've ever seen, maybe 0.050" pitch. That wraps around the needle's
pivot shaft. Here's a photo:
https://www.flickr.com/photos/16972296@N08/53916400376/in/dateposted-public/ >> (Sorry, the "tall thin post" is in shadow.)
The left end of the lever system is not a pivot point, but instead is a
rather wide brass stamping. I'd think that part could be made bimetallic
to provide temperature compensation.
--
- Frank Krygowski
Remember that ALL metals expand when heated but they expand at different rates so the mechanism has to correct the expansion of one metal against the expansion of the other for compensation so there has to be a mechanism that puts one point of rotationagainst another.
I wish that Liebermann would stop trying to be an expert at things he doesn't understand. He said that my way of using a pulse width to measure a line length so that you can zero in on the reflection point is wrong
but offered NO alternative
and then just the other day showed a TV90 and pretended that to be the alternative.
He has NO idea of how a TV90 works
which just happens to be a sophisticated copy of my way that is used to find cable faults in underground lines. Tektronics makes the TV100 which is a further sophistication.
He did the same thing when I wrote the formula of how altitude via air pressure is calculated. He writes the same thing and claims that I am wrong because it doesn't include compensation. If sea level pressure is unchanged there needs be nocompensation.
And you can't be in two places at one time. Wait, Lieberrmann can, just ask him.I used Campy 12 speed and Shimano Di2) because it is good enough for the way in which I ride. Your 7 speeds are fine for you. We agree to disagree about helmets and bike lanes. As long as you do not oppose people's choices in your state, that's good
The world is simulaneously complicated and simple. The deeper you look the more complicated it becomes but for most things a very simple observation is all you need. You are happy with your steel bike. I prefer a more complex bike. I use 10 speed (once
May you live to a healthy old age in a time of the party of Lincoln.
On 11/8/2024 3:59 PM, Zen Cycle wrote:
New meds?
That's a possibility. _Something_ has certainly happened to Tom in the
last few days!
Remember that ALL metals expand when heated but they expand...
On Sat, 09 Nov 2024 21:15:25 GMT, cyclintom <cyclintom@yahoo.com>will support Youngstown.
wrote:
And once again, he who would be Jobst and ian't, comments. Now that Trump is in office, we will actuLLY have job growth and not the Frank type of Democrat lies about it. That means people won't be seeking college degrees in the sort of numbers that
Tom. You don't understand how education works. When the economy is
good and there are plenty of jobs, you work, invest, and make money.
When the economy is not-so-good, and jobs are scarce, you go to
college so that when the economy eventually recovers, you will be
first in line for the newly created jobs.
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558
On Mon Nov 11 11:47:18 2024 Jeff Liebermann wrote:will support Youngstown.
On Sat, 09 Nov 2024 21:15:25 GMT, cyclintom <cyclintom@yahoo.com>
wrote:
And once again, he who would be Jobst and ian't, comments. Now that Trump is in office, we will actuLLY have job growth and not the Frank type of Democrat lies about it. That means people won't be seeking college degrees in the sort of numbers that
Gavin Loathsome doesn't cut your welfare in order to buy new cars for illegal aliens.
Tom. You don't understand how education works. When the economy is
good and there are plenty of jobs, you work, invest, and make money.
When the economy is not-so-good, and jobs are scarce, you go to
college so that when the economy eventually recovers, you will be
first in line for the newly created jobs.
Liebermann, you are a fool, HERE is the way that education works - you STUDY a book. You don't need to pay some ass like Krygowski to assign chapters. You got NOTHING out of your college education. And by reading books I got wealthy. Just hope that
On Fri, 15 Nov 2024 16:42:55 GMT, cyclintom <cyclintom@yahoo.com>will support Youngstown.
wrote:
On Mon Nov 11 11:47:18 2024 Jeff Liebermann wrote:
On Sat, 09 Nov 2024 21:15:25 GMT, cyclintom <cyclintom@yahoo.com>
wrote:
And once again, he who would be Jobst and ian't, comments. Now that Trump is in office, we will actuLLY have job growth and not the Frank type of Democrat lies about it. That means people won't be seeking college degrees in the sort of numbers that
Gavin Loathsome doesn't cut your welfare in order to buy new cars for illegal aliens.
Tom. You don't understand how education works. When the economy is
good and there are plenty of jobs, you work, invest, and make money.
When the economy is not-so-good, and jobs are scarce, you go to
college so that when the economy eventually recovers, you will be
first in line for the newly created jobs.
Liebermann, you are a fool, HERE is the way that education works - you STUDY a book. You don't need to pay some ass like Krygowski to assign chapters. You got NOTHING out of your college education. And by reading books I got wealthy. Just hope that
That's amazing. When you were working, when did you find the time to
read (or study) a book?
10/18/2024
<https://rec.bicycles.tech.narkive.com/twndhAxc/selling-used-bikes >
(article missing in archive).
Message-ID: <2BAQO.251408$EEm7.40885@fx16.iad>
"When I worked a job, I NEVER had time for anything other than work"
I think I can guess which books you were reading (i.e. get rich
quick):
<https://www.google.com/search?q=books+to+get+rich+quick>
You also went to sleep and discovered that you had designed a
successful product (presumably in your sleep). No book reading
required:
05/04/2023 <https://groups.google.com/g/rec.bicycles.tech/c/5dKZ-X891uI/m/bR5r_CZSBQAJ "I was pretty sure that I had worked for Varian and talking to one of
their retired employees I guess I designed and programmed a Gas
Spectrometer for them."
06/19/2023 <https://groups.google.com/g/rec.bicycles.tech/c/9WEuMylDquc/m/Guv7NHdsAwAJ> "Just this morning I awoke remembering I worked for Professor Archie
Stanley at Diablo Research."
On 11/15/2024 11:14 PM, Jeff Liebermann wrote:will support Youngstown.
On Fri, 15 Nov 2024 16:42:55 GMT, cyclintom <cyclintom@yahoo.com>
wrote:
On Mon Nov 11 11:47:18 2024 Jeff Liebermann wrote:
On Sat, 09 Nov 2024 21:15:25 GMT, cyclintom <cyclintom@yahoo.com>
wrote:
And once again, he who would be Jobst and ian't, comments. Now that Trump is in office, we will actuLLY have job growth and not the Frank type of Democrat lies about it. That means people won't be seeking college degrees in the sort of numbers that
Gavin Loathsome doesn't cut your welfare in order to buy new cars for illegal aliens.
Tom. You don't understand how education works. When the economy is
good and there are plenty of jobs, you work, invest, and make money.
When the economy is not-so-good, and jobs are scarce, you go to
college so that when the economy eventually recovers, you will be
first in line for the newly created jobs.
Liebermann, you are a fool, HERE is the way that education works - you STUDY a book. You don't need to pay some ass like Krygowski to assign chapters. You got NOTHING out of your college education. And by reading books I got wealthy. Just hope that
That's amazing. When you were working, when did you find the time to
read (or study) a book?
10/18/2024
<https://rec.bicycles.tech.narkive.com/twndhAxc/selling-used-bikes >
(article missing in archive).
Message-ID: <2BAQO.251408$EEm7.40885@fx16.iad>
"When I worked a job, I NEVER had time for anything other than work"
I think I can guess which books you were reading (i.e. get rich
quick):
<https://www.google.com/search?q=books+to+get+rich+quick>
You also went to sleep and discovered that you had designed a
successful product (presumably in your sleep). No book reading
required:
05/04/2023
<https://groups.google.com/g/rec.bicycles.tech/c/5dKZ-X891uI/m/bR5r_CZSBQAJ >> "I was pretty sure that I had worked for Varian and talking to one of
their retired employees I guess I designed and programmed a Gas
Spectrometer for them."
06/19/2023
<https://groups.google.com/g/rec.bicycles.tech/c/9WEuMylDquc/m/Guv7NHdsAwAJ> >> "Just this morning I awoke remembering I worked for Professor Archie
Stanley at Diablo Research."
Not only did he read _every_ book in three libraries, but he worked at >Tality(?) for 4 years, where they allegedly offered him a promotion into >management if he got a BS in something (using a more colloquial
definition of BS, apparently). He then proceeded to get that 4-year
degree in less than 4 years while working at Tality for 4 years full-time.
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