On Wed, 21 Sep 2022 11:26:10 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

>On Wed, 21 Sep 2022 13:29:31 -0400, Catrike Rider
><soloman@drafting.not> wrote:
>
>>On Wed, 21 Sep 2022 09:53:02 -0700, Jeff Liebermann <jeffl@cruzio.com>
>>wrote:
>>
>>>On Tue, 20 Sep 2022 04:51:55 -0700 (PDT), "funkma...@hotmail.com"
>>><funkmasterxx@hotmail.com> wrote:
>>>
>>>>This is a short MTB trail in the park I frequent. It's about 100 yards long and has a 20% average grade. The KOM belongs to a guy whose computer logged him doing it in 3 seconds,, or 73 mph. It's a sketchy part of the woods for GPS reception, so all of the top ten efforts are under 5 seconds, 10th place is 5 seconds, or 43 mph - for a trail up a 20% average grade.
>>>
>>>Erratic GPS reception is going to be a non-problem if we could ever
>>>get a GPS with UDR (Untethered Dead Reckoning).
>>><https://www.u-blox.com/en/technologies/udr-untethered-dead-reckoning-0>
>>>Basically, these use inertial navigation (accelerometer and compass)
>>>to fill in the gaps between GPS fixes. With UDR, you could get
>>>accurate speeds and positions while riding inside a tunnel. UDR
>>>products are available, but not (yet) in a phone suitable for running
>>>the Strava app:
>>><https://www.u-blox.com/en/press-release/navilock%E2%80%99s-new-gnss-receiver-series-features-u-blox%E2%80%99s-untethered-3d-dead-reckoning-udr>
>>>NMEA-0183 to RS-232 via USB converters are available that will talk to
>>>a smartphone, but the dongle and wiring mess and the added external
>>>GPS receiver combination are probably not suitable for cycling.
>
>>I've been using GPS for many years, for sailing, driving, hiking,
>>kayaking, and now bicycling. When I was sailing, I depended on it to
>>avoid reefs and sandbars and to safely put me through to anchorages
>>and docks. I've never noticed any inaccuracies beyond a few feet, and
>>even then, only rarely. I know many modern crop farmers use it to
>>guide their planting, spraying, and harvesting endeavors. The military
>>uses it for, among other things, to guide missile attacks. When I
>>ride, I have three GPS devices, my watch, my cellphone, and my Garmin
>>bike computer. I don't need any of them, but it's nice to be able to
>>see my speed on a map at any point in my ride.
>
>I'm not talking about accuracy. I'm talking about getting enough GPS
>location fixes (not fixies) and speed measurements to connect the
>dots. GPS uses Doppler shift in order to determine speed, which is
>VERY accurate. It's far more accurate than distance between fixes
>divided by time. If you want details, I wrote something on the topic
>in RBT a few months ago. I can try to find my rants if you're
>interested. When riding through urban jungles, forests, and GPS dead
>zones, the problem isn't accuracy, but rather getting enough fixes to
>calculate any kind of route or speed.
>
>UDR (untethered dead reckoning) will do the job where there are no GPS
>signals. It won't do anything for your sailing, which is generally in
>high signal areas. It's marginal for hiking, depending on where you
>like to hike. If you're hiking through a canyon, UDR will be a big
>help. If you're climbing a mountain, with a good view of the sky, it
>won't be much use. For driving, UDR will help in urban canyons,
>tunnels, and under bridges.
>
>I'm quite familiar with older GPS technology used in farming. The
>accuracy of such systems is dependent on using differential GPS
>transmitters located on the ground near the farm. Accuracy is +/- a
>few centimeters. I have some old AutoFarm hardware that was used for
>the plowing:
><https://precisionagricultu.re/autofarm-gps-precision-farming-paradyme/>
>There's no need for UDR on a farm, where signal obstructions are
>unlikely. The military has the money to buy all the latest toys. They
>probably already have UDR GPS receivers. However, UDR won't do
>anything useful in a missile or airplane, which presumably have the
>best possible view of the sky.

I understand... Thanks for the clarification I do ride through some
heavily wooded areas and haven't noticed any loss of GPS there The
only times my Garmin tells me it lost satilite connections is a couple
of places on bridges where there was a lot of overhead metal
structure. I don't know how long it needs to lose connection before it
lets me know.

On Wed, 21 Sep 2022 11:43:16 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

>On Wed, 21 Sep 2022 10:45:56 -0700 (PDT), Tom Kunich
><cyclintom@gmail.com> wrote:
>
>>The maximum inaccuracy of civilian GPS is 13 feet plus or minus.
>
>Wrong. Please stop inventing numbers for your convenience. Show your
>source or your calculations and I might believe your numbers.
>
>>This only occurs when all of the satellites are on one horizon or the other.
>
>Wrong. The Doppler shift change from a given satellite is zero at
>both the horizon and at zenith (directly overhead). When all the
>satellite are at the horizon, you nothing.
>
>>This rarely happens so the normal accuracy is very close.
>
>Actually, it does happen quite often in a building with lots of
>windows and a roof impervious to RF.
>
>>Military GPS corrects for all of the inaccuracies and has
>>accuracies of about an inch all the time.
>
>No, it doesn't. All that a "military" GPS does is use additional
>encrypted "military only" frequencies which are used along with the
>civilian frequencies to provide a better correction for atmospheric
>diffraction.
>
>>This is why nuclear war is impractical from the start. All of
>>the government leaders would be wiped out from the start and it
>>would leave no one but military lower ranks that know that any
>>further war is fruitless.
>
>Have you considered a career writing science fiction? That would make
>a tolerable plot for a movie.
>
>>Lou takes the position that my Garmin reported 87 mph was
>>a freak error of the GPS. I tend to side with him but I am
>>not as sure as he is.
>
>Perhaps if you searched for a similar problem? I posted this
>previously, but apparently you were too busy complaining to notice.
><https://forums.garmin.com/apps-software/mobile-apps-web/f/garmin-connect-web/52217/max-speed-error>
>"Max speed reported was 82 mph!"
>
>>Having worked on instruments like a GPS I would program them
>>to average many readings before producing such an outlandish
>>number. This suggests that perhaps that speed was correct.
>>But it would only be acceptable if repeated at least with a
>>near number.
>
>Baloney, but I don't have time to fix your mistakes. Gone for lunch
>with some friends.

For what's worth, my Garmin does not normally depend on GPS to
calulate my speed and Distance. I have a sensor wrapped around one of
my front axles that transmits rotation count. It does use GPS to
recalulate length of a wheel rotation. If I lose the sensor (battery),
the GPS will take over those functions and they are not nearly as
accurate.

On Wednesday, September 21, 2022 at 11:56:44 AM UTC-7, Catrike Rider wrote:
> On Wed, 21 Sep 2022 11:43:16 -0700, Jeff Liebermann <je...@cruzio.com>
> wrote:
> >On Wed, 21 Sep 2022 10:45:56 -0700 (PDT), Tom Kunich
> ><cycl...@gmail.com> wrote:
> >
> >>The maximum inaccuracy of civilian GPS is 13 feet plus or minus.
> >
> >Wrong. Please stop inventing numbers for your convenience. Show your
> >source or your calculations and I might believe your numbers.
> >
> >>This only occurs when all of the satellites are on one horizon or the other.
> >
> >Wrong. The Doppler shift change from a given satellite is zero at
> >both the horizon and at zenith (directly overhead). When all the
> >satellite are at the horizon, you nothing.
> >
> >>This rarely happens so the normal accuracy is very close.
> >
> >Actually, it does happen quite often in a building with lots of
> >windows and a roof impervious to RF.
> >
> >>Military GPS corrects for all of the inaccuracies and has
> >>accuracies of about an inch all the time.
> >
> >No, it doesn't. All that a "military" GPS does is use additional
> >encrypted "military only" frequencies which are used along with the
> >civilian frequencies to provide a better correction for atmospheric
> >diffraction.
> >
> >>This is why nuclear war is impractical from the start. All of
> >>the government leaders would be wiped out from the start and it
> >>would leave no one but military lower ranks that know that any
> >>further war is fruitless.
> >
> >Have you considered a career writing science fiction? That would make
> >a tolerable plot for a movie.
> >
> >>Lou takes the position that my Garmin reported 87 mph was
> >>a freak error of the GPS. I tend to side with him but I am
> >>not as sure as he is.
> >
> >Perhaps if you searched for a similar problem? I posted this
> >previously, but apparently you were too busy complaining to notice.
> ><https://forums.garmin.com/apps-software/mobile-apps-web/f/garmin-connect-web/52217/max-speed-error>
> >"Max speed reported was 82 mph!"
> >
> >>Having worked on instruments like a GPS I would program them
> >>to average many readings before producing such an outlandish
> >>number. This suggests that perhaps that speed was correct.
> >>But it would only be acceptable if repeated at least with a
> >>near number.
> >
> >Baloney, but I don't have time to fix your mistakes. Gone for lunch
> >with some friends.
> For what's worth, my Garmin does not normally depend on GPS to
> calulate my speed and Distance. I have a sensor wrapped around one of
> my front axles that transmits rotation count. It does use GPS to
> recalulate length of a wheel rotation. If I lose the sensor (battery),
> the GPS will take over those functions and they are not nearly as
> accurate.

As usual you cannot believe anything that Liebermann says. Doppler shift is not measureable in most areas. If you set your Garmin up to use ONLY GPS for speed and distance when you turn it on you can see the speed of the satellite across the sky over you as you show anywhere from .1 to ,25 mph and sometimes higher. This is why you use sensors for speed and distance. The software automatically corrects for the wheel diameter and is more accurate the further the distance is you travel.

As for doppler shift - https://www.researchgate.net/figure/Doppler-Shift-Prediction-Accuracy_fig2_352548023 As you can see that it is not accurate without long term averaging. I worked on the doppler for bombing control on B52's and while it is useful it is hardly "very accurate".

On Wed, 21 Sep 2022 14:09:20 -0700 (PDT), Tom Kunich
<cyclintom@gmail.com> wrote:

>On Wednesday, September 21, 2022 at 11:56:44 AM UTC-7, Catrike Rider wrote:
>> On Wed, 21 Sep 2022 11:43:16 -0700, Jeff Liebermann <je...@cruzio.com>
>> wrote:
>> >On Wed, 21 Sep 2022 10:45:56 -0700 (PDT), Tom Kunich
>> ><cycl...@gmail.com> wrote:
>> >
>> >>The maximum inaccuracy of civilian GPS is 13 feet plus or minus.
>> >
>> >Wrong. Please stop inventing numbers for your convenience. Show your
>> >source or your calculations and I might believe your numbers.
>> >
>> >>This only occurs when all of the satellites are on one horizon or the other.
>> >
>> >Wrong. The Doppler shift change from a given satellite is zero at
>> >both the horizon and at zenith (directly overhead). When all the
>> >satellite are at the horizon, you nothing.
>> >
>> >>This rarely happens so the normal accuracy is very close.
>> >
>> >Actually, it does happen quite often in a building with lots of
>> >windows and a roof impervious to RF.
>> >
>> >>Military GPS corrects for all of the inaccuracies and has
>> >>accuracies of about an inch all the time.
>> >
>> >No, it doesn't. All that a "military" GPS does is use additional
>> >encrypted "military only" frequencies which are used along with the
>> >civilian frequencies to provide a better correction for atmospheric
>> >diffraction.
>> >
>> >>This is why nuclear war is impractical from the start. All of
>> >>the government leaders would be wiped out from the start and it
>> >>would leave no one but military lower ranks that know that any
>> >>further war is fruitless.
>> >
>> >Have you considered a career writing science fiction? That would make
>> >a tolerable plot for a movie.
>> >
>> >>Lou takes the position that my Garmin reported 87 mph was
>> >>a freak error of the GPS. I tend to side with him but I am
>> >>not as sure as he is.
>> >
>> >Perhaps if you searched for a similar problem? I posted this
>> >previously, but apparently you were too busy complaining to notice.
>> ><https://forums.garmin.com/apps-software/mobile-apps-web/f/garmin-connect-web/52217/max-speed-error>
>> >"Max speed reported was 82 mph!"
>> >
>> >>Having worked on instruments like a GPS I would program them
>> >>to average many readings before producing such an outlandish
>> >>number. This suggests that perhaps that speed was correct.
>> >>But it would only be acceptable if repeated at least with a
>> >>near number.
>> >
>> >Baloney, but I don't have time to fix your mistakes. Gone for lunch
>> >with some friends.
>> For what's worth, my Garmin does not normally depend on GPS to
>> calulate my speed and Distance. I have a sensor wrapped around one of
>> my front axles that transmits rotation count. It does use GPS to
>> recalulate length of a wheel rotation. If I lose the sensor (battery),
>> the GPS will take over those functions and they are not nearly as
>> accurate.

>Doppler shift is not measureable in most areas. If you set your Garmin up to use ONLY GPS for speed and distance when you turn it on you can see the speed of the satellite across the sky over you as you show anywhere from .1 to ,25 mph and sometimes higher.

Wrong again. When you're not moving, the small residual movement is
caused by GPS timing uncertainty and clock jitter. If you plot your
positions on a scatter plot, you get something like this:
<https://www.visualgps.net/VisualGPSView/images/ssScatter.png>

>This is why you use sensors for speed and distance. The software
>automatically corrects for the wheel diameter and is more accurate
>the further the distance is you travel.

That works badly if you loose tire pressure or if you didn't calibrate
it correctly, which can change the effective tire diameter.

>As for doppler shift - https://www.researchgate.net/figure/Doppler-Shift-Prediction-Accuracy_fig2_352548023
>As you can see that it is not accurate without long term averaging.

Wrong. What I see is that the author demonstrated that averaging
improves positional accuracy. That works great if you're not moving
such as is common with various surveying apps. Averaging doesn't work
while moving, unless you're going really slow. Please find a link
that substantiates what you're claiming and please stop confusing
positional accuracy with velocity accuracy.

>I worked on the doppler for bombing control on B52's and while it
>is useful it is hardly "very accurate".

Wrong. See:
<https://www.onosokki.co.jp/English/hp_e/products/keisoku/automotive/lc8_principle.htm>
"In this method, the speed of the moving object can be calculated
extremely more precisely than the calculation method using the amount
of position change, because it receives almost none of the influence
from the ionosphere. The accuracy of its horizontal component is
0.003 m/s when 2 sigma, 0.08 m/s when 3 sigma".

Remember, this is about velocity (speed) and not position accuracy.
0.08 meters/sec speed accuracy is far more accurate than anything that
uses distance divided by time to calculate velocity.

Notice that the above URL is about using UDR (unteathered dead
reconning) to improve vehicular GPS when there are insufficient number
of satellites to obtain a postition or velocity. See the illustration
at the bottom of the page showing the signal drop out.

100% perfect score again. Everything you have to offer is wrong.

--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

On Wed, 21 Sep 2022 10:08:24 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

>On Wed, 21 Sep 2022 06:07:25 +0700, John B. <slocombjb@gmail.com>
>wrote:
>>A good friend who sails told me that one of his favorite anchorages in
>>the Philippines is about 100 meters on dry land, according to the GPS.
>
>Have your friend check what datum his maps and GPS are using. They
>should be the same. The default for all GPS receivers is WGS 84. He
>might be using PRS92 or one of the older datums for the area, such as
>Luzon 1911. Presumably, he's in one of these 5 zones:
><https://epsg.io/3121>
><https://epsg.io/3122>
><https://epsg.io/3123>
><https://epsg.io/3124>
><https://epsg.io/3125>
>"Modernization of the PHILIPPINE GEODETIC REFERENCE SYSTEM"
><https://www.namria.gov.ph/jdownloads/Others/StratPlan_Modernization.pdf>

This was quite a number of years ago but he probably was aware of map
and GPS datum as this was after he made his first circumnavigation, so
it wasn't as though he was a novice (:-)
--
Cheers,

John B.

On Wed, 21 Sep 2022 11:26:10 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

>On Wed, 21 Sep 2022 13:29:31 -0400, Catrike Rider
><soloman@drafting.not> wrote:
>
>>On Wed, 21 Sep 2022 09:53:02 -0700, Jeff Liebermann <jeffl@cruzio.com>
>>wrote:
>>
>>>On Tue, 20 Sep 2022 04:51:55 -0700 (PDT), "funkma...@hotmail.com"
>>><funkmasterxx@hotmail.com> wrote:
>>>
>>>>This is a short MTB trail in the park I frequent. It's about 100 yards long and has a 20% average grade. The KOM belongs to a guy whose computer logged him doing it in 3 seconds,, or 73 mph. It's a sketchy part of the woods for GPS reception, so all of the top ten efforts are under 5 seconds, 10th place is 5 seconds, or 43 mph - for a trail up a 20% average grade.
>>>
>>>Erratic GPS reception is going to be a non-problem if we could ever
>>>get a GPS with UDR (Untethered Dead Reckoning).
>>><https://www.u-blox.com/en/technologies/udr-untethered-dead-reckoning-0>
>>>Basically, these use inertial navigation (accelerometer and compass)
>>>to fill in the gaps between GPS fixes. With UDR, you could get
>>>accurate speeds and positions while riding inside a tunnel. UDR
>>>products are available, but not (yet) in a phone suitable for running
>>>the Strava app:
>>><https://www.u-blox.com/en/press-release/navilock%E2%80%99s-new-gnss-receiver-series-features-u-blox%E2%80%99s-untethered-3d-dead-reckoning-udr>
>>>NMEA-0183 to RS-232 via USB converters are available that will talk to
>>>a smartphone, but the dongle and wiring mess and the added external
>>>GPS receiver combination are probably not suitable for cycling.
>
>>I've been using GPS for many years, for sailing, driving, hiking,
>>kayaking, and now bicycling. When I was sailing, I depended on it to
>>avoid reefs and sandbars and to safely put me through to anchorages
>>and docks. I've never noticed any inaccuracies beyond a few feet, and
>>even then, only rarely. I know many modern crop farmers use it to
>>guide their planting, spraying, and harvesting endeavors. The military
>>uses it for, among other things, to guide missile attacks. When I
>>ride, I have three GPS devices, my watch, my cellphone, and my Garmin
>>bike computer. I don't need any of them, but it's nice to be able to
>>see my speed on a map at any point in my ride.
>
>I'm not talking about accuracy. I'm talking about getting enough GPS
>location fixes (not fixies) and speed measurements to connect the
>dots. GPS uses Doppler shift in order to determine speed, which is
>VERY accurate. It's far more accurate than distance between fixes
>divided by time. If you want details, I wrote something on the topic
>in RBT a few months ago. I can try to find my rants if you're
>interested. When riding through urban jungles, forests, and GPS dead
>zones, the problem isn't accuracy, but rather getting enough fixes to
>calculate any kind of route or speed.
>
>UDR (untethered dead reckoning) will do the job where there are no GPS
>signals. It won't do anything for your sailing, which is generally in
>high signal areas. It's marginal for hiking, depending on where you
>like to hike. If you're hiking through a canyon, UDR will be a big
>help. If you're climbing a mountain, with a good view of the sky, it
>won't be much use. For driving, UDR will help in urban canyons,
>tunnels, and under bridges.
>
>I'm quite familiar with older GPS technology used in farming. The
>accuracy of such systems is dependent on using differential GPS
>transmitters located on the ground near the farm. Accuracy is +/- a
>few centimeters. I have some old AutoFarm hardware that was used for
>the plowing:
><https://precisionagricultu.re/autofarm-gps-precision-farming-paradyme/>
>There's no need for UDR on a farm, where signal obstructions are
>unlikely. The military has the money to buy all the latest toys. They
>probably already have UDR GPS receivers. However, UDR won't do
>anything useful in a missile or airplane, which presumably have the
>best possible view of the sky.

I was going to ask you about that as way back when I was involved in
oil well drilling in West Papua (Irian Jaya) which were located
referenced to seismic locations that the Seismic guys told us were
accurate to feet.
--
Cheers,

John B.

On Wed, 21 Sep 2022 14:49:21 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

>On Wed, 21 Sep 2022 14:09:20 -0700 (PDT), Tom Kunich
><cyclintom@gmail.com> wrote:
>
>>On Wednesday, September 21, 2022 at 11:56:44 AM UTC-7, Catrike Rider wrote:
>>> On Wed, 21 Sep 2022 11:43:16 -0700, Jeff Liebermann <je...@cruzio.com>
>>> wrote:
>>> >On Wed, 21 Sep 2022 10:45:56 -0700 (PDT), Tom Kunich
>>> ><cycl...@gmail.com> wrote:
>>> >
>>> >>The maximum inaccuracy of civilian GPS is 13 feet plus or minus.
>>> >
>>> >Wrong. Please stop inventing numbers for your convenience. Show your
>>> >source or your calculations and I might believe your numbers.
>>> >
>>> >>This only occurs when all of the satellites are on one horizon or the other.
>>> >
>>> >Wrong. The Doppler shift change from a given satellite is zero at
>>> >both the horizon and at zenith (directly overhead). When all the
>>> >satellite are at the horizon, you nothing.
>>> >
>>> >>This rarely happens so the normal accuracy is very close.
>>> >
>>> >Actually, it does happen quite often in a building with lots of
>>> >windows and a roof impervious to RF.
>>> >
>>> >>Military GPS corrects for all of the inaccuracies and has
>>> >>accuracies of about an inch all the time.
>>> >
>>> >No, it doesn't. All that a "military" GPS does is use additional
>>> >encrypted "military only" frequencies which are used along with the
>>> >civilian frequencies to provide a better correction for atmospheric
>>> >diffraction.
>>> >
>>> >>This is why nuclear war is impractical from the start. All of
>>> >>the government leaders would be wiped out from the start and it
>>> >>would leave no one but military lower ranks that know that any
>>> >>further war is fruitless.
>>> >
>>> >Have you considered a career writing science fiction? That would make
>>> >a tolerable plot for a movie.
>>> >
>>> >>Lou takes the position that my Garmin reported 87 mph was
>>> >>a freak error of the GPS. I tend to side with him but I am
>>> >>not as sure as he is.
>>> >
>>> >Perhaps if you searched for a similar problem? I posted this
>>> >previously, but apparently you were too busy complaining to notice.
>>> ><https://forums.garmin.com/apps-software/mobile-apps-web/f/garmin-connect-web/52217/max-speed-error>
>>> >"Max speed reported was 82 mph!"
>>> >
>>> >>Having worked on instruments like a GPS I would program them
>>> >>to average many readings before producing such an outlandish
>>> >>number. This suggests that perhaps that speed was correct.
>>> >>But it would only be acceptable if repeated at least with a
>>> >>near number.
>>> >
>>> >Baloney, but I don't have time to fix your mistakes. Gone for lunch
>>> >with some friends.
>>> For what's worth, my Garmin does not normally depend on GPS to
>>> calulate my speed and Distance. I have a sensor wrapped around one of
>>> my front axles that transmits rotation count. It does use GPS to
>>> recalulate length of a wheel rotation. If I lose the sensor (battery),
>>> the GPS will take over those functions and they are not nearly as
>>> accurate.
>
>>Doppler shift is not measureable in most areas. If you set your Garmin up to use ONLY GPS for speed and distance when you turn it on you can see the speed of the satellite across the sky over you as you show anywhere from .1 to ,25 mph and sometimes higher.
>
>Wrong again. When you're not moving, the small residual movement is
>caused by GPS timing uncertainty and clock jitter. If you plot your
>positions on a scatter plot, you get something like this:
><https://www.visualgps.net/VisualGPSView/images/ssScatter.png>
>
>>This is why you use sensors for speed and distance. The software
>>automatically corrects for the wheel diameter and is more accurate
>>the further the distance is you travel.
>
>That works badly if you loose tire pressure or if you didn't calibrate
>it correctly, which can change the effective tire diameter.
>
>>As for doppler shift - https://www.researchgate.net/figure/Doppler-Shift-Prediction-Accuracy_fig2_352548023
>>As you can see that it is not accurate without long term averaging.
>
>Wrong. What I see is that the author demonstrated that averaging
>improves positional accuracy. That works great if you're not moving
>such as is common with various surveying apps. Averaging doesn't work
>while moving, unless you're going really slow. Please find a link
>that substantiates what you're claiming and please stop confusing
>positional accuracy with velocity accuracy.
>
>>I worked on the doppler for bombing control on B52's and while it
>>is useful it is hardly "very accurate".
>
>Wrong. See:
><https://www.onosokki.co.jp/English/hp_e/products/keisoku/automotive/lc8_principle.htm>
>"In this method, the speed of the moving object can be calculated
>extremely more precisely than the calculation method using the amount
>of position change, because it receives almost none of the influence
>from the ionosphere. The accuracy of its horizontal component is
>0.003 m/s when 2 sigma, 0.08 m/s when 3 sigma".
>
>Remember, this is about velocity (speed) and not position accuracy.
>0.08 meters/sec speed accuracy is far more accurate than anything that
>uses distance divided by time to calculate velocity.
>
>Notice that the above URL is about using UDR (unteathered dead
>reconning) to improve vehicular GPS when there are insufficient number
>of satellites to obtain a postition or velocity. See the illustration
>at the bottom of the page showing the signal drop out.
>

>100% perfect score again. Everything you have to offer is wrong.

And I'll bet this came as a great surprise?
--
Cheers,

John B.

On Wed, 21 Sep 2022 14:49:21 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

>On Wed, 21 Sep 2022 14:09:20 -0700 (PDT), Tom Kunich
><cyclintom@gmail.com> wrote:
>
>>On Wednesday, September 21, 2022 at 11:56:44 AM UTC-7, Catrike Rider wrote:
>>> On Wed, 21 Sep 2022 11:43:16 -0700, Jeff Liebermann <je...@cruzio.com>
>>> wrote:
>>> >On Wed, 21 Sep 2022 10:45:56 -0700 (PDT), Tom Kunich
>>> ><cycl...@gmail.com> wrote:
>>> >
>>> >>The maximum inaccuracy of civilian GPS is 13 feet plus or minus.
>>> >
>>> >Wrong. Please stop inventing numbers for your convenience. Show your
>>> >source or your calculations and I might believe your numbers.
>>> >
>>> >>This only occurs when all of the satellites are on one horizon or the other.
>>> >
>>> >Wrong. The Doppler shift change from a given satellite is zero at
>>> >both the horizon and at zenith (directly overhead). When all the
>>> >satellite are at the horizon, you nothing.
>>> >
>>> >>This rarely happens so the normal accuracy is very close.
>>> >
>>> >Actually, it does happen quite often in a building with lots of
>>> >windows and a roof impervious to RF.
>>> >
>>> >>Military GPS corrects for all of the inaccuracies and has
>>> >>accuracies of about an inch all the time.
>>> >
>>> >No, it doesn't. All that a "military" GPS does is use additional
>>> >encrypted "military only" frequencies which are used along with the
>>> >civilian frequencies to provide a better correction for atmospheric
>>> >diffraction.
>>> >
>>> >>This is why nuclear war is impractical from the start. All of
>>> >>the government leaders would be wiped out from the start and it
>>> >>would leave no one but military lower ranks that know that any
>>> >>further war is fruitless.
>>> >
>>> >Have you considered a career writing science fiction? That would make
>>> >a tolerable plot for a movie.
>>> >
>>> >>Lou takes the position that my Garmin reported 87 mph was
>>> >>a freak error of the GPS. I tend to side with him but I am
>>> >>not as sure as he is.
>>> >
>>> >Perhaps if you searched for a similar problem? I posted this
>>> >previously, but apparently you were too busy complaining to notice.
>>> ><https://forums.garmin.com/apps-software/mobile-apps-web/f/garmin-connect-web/52217/max-speed-error>
>>> >"Max speed reported was 82 mph!"
>>> >
>>> >>Having worked on instruments like a GPS I would program them
>>> >>to average many readings before producing such an outlandish
>>> >>number. This suggests that perhaps that speed was correct.
>>> >>But it would only be acceptable if repeated at least with a
>>> >>near number.
>>> >
>>> >Baloney, but I don't have time to fix your mistakes. Gone for lunch
>>> >with some friends.
>>> For what's worth, my Garmin does not normally depend on GPS to
>>> calulate my speed and Distance. I have a sensor wrapped around one of
>>> my front axles that transmits rotation count. It does use GPS to
>>> recalulate length of a wheel rotation. If I lose the sensor (battery),
>>> the GPS will take over those functions and they are not nearly as
>>> accurate.
>
>>Doppler shift is not measureable in most areas. If you set your Garmin up to use ONLY GPS for speed and distance when you turn it on you can see the speed of the satellite across the sky over you as you show anywhere from .1 to ,25 mph and sometimes higher.
>
>Wrong again. When you're not moving, the small residual movement is
>caused by GPS timing uncertainty and clock jitter. If you plot your
>positions on a scatter plot, you get something like this:
><https://www.visualgps.net/VisualGPSView/images/ssScatter.png>
>
>>This is why you use sensors for speed and distance. The software
>>automatically corrects for the wheel diameter and is more accurate
>>the further the distance is you travel.
>
>That works badly if you loose tire pressure or if you didn't calibrate
>it correctly, which can change the effective tire diameter.
>
>>As for doppler shift - https://www.researchgate.net/figure/Doppler-Shift-Prediction-Accuracy_fig2_352548023
>>As you can see that it is not accurate without long term averaging.
>
>Wrong. What I see is that the author demonstrated that averaging
>improves positional accuracy. That works great if you're not moving
>such as is common with various surveying apps. Averaging doesn't work
>while moving, unless you're going really slow. Please find a link
>that substantiates what you're claiming and please stop confusing
>positional accuracy with velocity accuracy.
>
>>I worked on the doppler for bombing control on B52's and while it
>>is useful it is hardly "very accurate".
>
>Wrong. See:
><https://www.onosokki.co.jp/English/hp_e/products/keisoku/automotive/lc8_principle.htm>
>"In this method, the speed of the moving object can be calculated
>extremely more precisely than the calculation method using the amount
>of position change, because it receives almost none of the influence
>from the ionosphere. The accuracy of its horizontal component is
>0.003 m/s when 2 sigma, 0.08 m/s when 3 sigma".
>
>Remember, this is about velocity (speed) and not position accuracy.
>0.08 meters/sec speed accuracy is far more accurate than anything that
>uses distance divided by time to calculate velocity.
>
>Notice that the above URL is about using UDR (unteathered dead
>reconning) to improve vehicular GPS when there are insufficient number
>of satellites to obtain a postition or velocity. See the illustration
>at the bottom of the page showing the signal drop out.
>
>100% perfect score again. Everything you have to offer is wrong.

You might have noticed Tommy mentioning taking a "Carbamazepine"
tablet. I googled this medication and it is often proscribed for
"Bipolar disorder" which is described as " a mental health condition
that affects your moods, which can swing from one extreme to another.
It used to be known as manic depression" and during the maniac phase
the following are mentioned as common

talking very quickly
feeling self-important
feeling full of great new ideas and having important plans
being easily distracted
being easily irritated or agitated
being delusional, having hallucinations and disturbed or illogical
thinking

--
Cheers,

John B.

On Wednesday, September 21, 2022 at 2:09:22 PM UTC-7, Tom Kunich wrote:
> On Wednesday, September 21, 2022 at 11:56:44 AM UTC-7, Catrike Rider wrote:
> > On Wed, 21 Sep 2022 11:43:16 -0700, Jeff Liebermann <je...@cruzio.com>
> > wrote:
> > >On Wed, 21 Sep 2022 10:45:56 -0700 (PDT), Tom Kunich
> > ><cycl...@gmail.com> wrote:
> > >
> > >>The maximum inaccuracy of civilian GPS is 13 feet plus or minus.
> > >
> > >Wrong. Please stop inventing numbers for your convenience. Show your
> > >source or your calculations and I might believe your numbers.
> > >
> > >>This only occurs when all of the satellites are on one horizon or the other.
> > >
> > >Wrong. The Doppler shift change from a given satellite is zero at
> > >both the horizon and at zenith (directly overhead). When all the
> > >satellite are at the horizon, you nothing.
> > >
> > >>This rarely happens so the normal accuracy is very close.
> > >
> > >Actually, it does happen quite often in a building with lots of
> > >windows and a roof impervious to RF.
> > >
> > >>Military GPS corrects for all of the inaccuracies and has
> > >>accuracies of about an inch all the time.
> > >
> > >No, it doesn't. All that a "military" GPS does is use additional
> > >encrypted "military only" frequencies which are used along with the
> > >civilian frequencies to provide a better correction for atmospheric
> > >diffraction.
> > >
> > >>This is why nuclear war is impractical from the start. All of
> > >>the government leaders would be wiped out from the start and it
> > >>would leave no one but military lower ranks that know that any
> > >>further war is fruitless.
> > >
> > >Have you considered a career writing science fiction? That would make
> > >a tolerable plot for a movie.
> > >
> > >>Lou takes the position that my Garmin reported 87 mph was
> > >>a freak error of the GPS. I tend to side with him but I am
> > >>not as sure as he is.
> > >
> > >Perhaps if you searched for a similar problem? I posted this
> > >previously, but apparently you were too busy complaining to notice.
> > ><https://forums.garmin.com/apps-software/mobile-apps-web/f/garmin-connect-web/52217/max-speed-error>
> > >"Max speed reported was 82 mph!"
> > >
> > >>Having worked on instruments like a GPS I would program them
> > >>to average many readings before producing such an outlandish
> > >>number. This suggests that perhaps that speed was correct.
> > >>But it would only be acceptable if repeated at least with a
> > >>near number.
> > >
> > >Baloney, but I don't have time to fix your mistakes. Gone for lunch
> > >with some friends.
> > For what's worth, my Garmin does not normally depend on GPS to
> > calulate my speed and Distance. I have a sensor wrapped around one of
> > my front axles that transmits rotation count. It does use GPS to
> > recalulate length of a wheel rotation. If I lose the sensor (battery),
> > the GPS will take over those functions and they are not nearly as
> > accurate.
> As usual you cannot believe anything that Liebermann says. Doppler shift is not measureable in most areas. If you set your Garmin up to use ONLY GPS for speed and distance when you turn it on you can see the speed of the satellite across the sky over you as you show anywhere from .1 to ,25 mph and sometimes higher. This is why you use sensors for speed and distance. The software automatically corrects for the wheel diameter and is more accurate the further the distance is you travel.
>
> As for doppler shift - https://www.researchgate.net/figure/Doppler-Shift-Prediction-Accuracy_fig2_352548023 As you can see that it is not accurate without long term averaging. I worked on the doppler for bombing control on B52's and while it is useful it is hardly "very accurate".

Since I was checking my Google mailbox there was Liebermann again being as stupid as humanly possible. What an ass - The B52D was manufactured in 1955 and 1956. I was in the Air Force from 1961 to 1967. Why do you suppose that stupid jackass is talking about GPS when the FIRST satellite wasn't launched until 1973 or so? He has turned into nothing but another copy of Slocum who knows nothing but can use Google like a possum. between the two of them I bet that they can get absolutely anything and everything wrong from the ACTUAL death count from Covid-19 which I showed you the CDC page on Covid-19 death count where there were only 8,000 killed by the illness that is less severe than seasonal flu. Do people die from it? Sure, they ALSO die by the thousands each bad flu year.

There isn't one thing that these dopes could get right if you paid them a million dollars to go to a physicist and ask him to explain it to them. A life of stupidity.

On Wed, 21 Sep 2022 17:17:18 -0700 (PDT), Tom Kunich
<cyclintom@gmail.com> wrote:

>On Wednesday, September 21, 2022 at 2:09:22 PM UTC-7, Tom Kunich wrote:
>> On Wednesday, September 21, 2022 at 11:56:44 AM UTC-7, Catrike Rider wrote:
>> > On Wed, 21 Sep 2022 11:43:16 -0700, Jeff Liebermann <je...@cruzio.com>
>> > wrote:
>> > >On Wed, 21 Sep 2022 10:45:56 -0700 (PDT), Tom Kunich
>> > ><cycl...@gmail.com> wrote:
>> > >
>> > >>The maximum inaccuracy of civilian GPS is 13 feet plus or minus.
>> > >
>> > >Wrong. Please stop inventing numbers for your convenience. Show your
>> > >source or your calculations and I might believe your numbers.
>> > >
>> > >>This only occurs when all of the satellites are on one horizon or the other.
>> > >
>> > >Wrong. The Doppler shift change from a given satellite is zero at
>> > >both the horizon and at zenith (directly overhead). When all the
>> > >satellite are at the horizon, you nothing.
>> > >
>> > >>This rarely happens so the normal accuracy is very close.
>> > >
>> > >Actually, it does happen quite often in a building with lots of
>> > >windows and a roof impervious to RF.
>> > >
>> > >>Military GPS corrects for all of the inaccuracies and has
>> > >>accuracies of about an inch all the time.
>> > >
>> > >No, it doesn't. All that a "military" GPS does is use additional
>> > >encrypted "military only" frequencies which are used along with the
>> > >civilian frequencies to provide a better correction for atmospheric
>> > >diffraction.
>> > >
>> > >>This is why nuclear war is impractical from the start. All of
>> > >>the government leaders would be wiped out from the start and it
>> > >>would leave no one but military lower ranks that know that any
>> > >>further war is fruitless.
>> > >
>> > >Have you considered a career writing science fiction? That would make
>> > >a tolerable plot for a movie.
>> > >
>> > >>Lou takes the position that my Garmin reported 87 mph was
>> > >>a freak error of the GPS. I tend to side with him but I am
>> > >>not as sure as he is.
>> > >
>> > >Perhaps if you searched for a similar problem? I posted this
>> > >previously, but apparently you were too busy complaining to notice.
>> > ><https://forums.garmin.com/apps-software/mobile-apps-web/f/garmin-connect-web/52217/max-speed-error>
>> > >"Max speed reported was 82 mph!"
>> > >
>> > >>Having worked on instruments like a GPS I would program them
>> > >>to average many readings before producing such an outlandish
>> > >>number. This suggests that perhaps that speed was correct.
>> > >>But it would only be acceptable if repeated at least with a
>> > >>near number.
>> > >
>> > >Baloney, but I don't have time to fix your mistakes. Gone for lunch
>> > >with some friends.
>> > For what's worth, my Garmin does not normally depend on GPS to
>> > calulate my speed and Distance. I have a sensor wrapped around one of
>> > my front axles that transmits rotation count. It does use GPS to
>> > recalulate length of a wheel rotation. If I lose the sensor (battery),
>> > the GPS will take over those functions and they are not nearly as
>> > accurate.
>> As usual you cannot believe anything that Liebermann says. Doppler shift is not measureable in most areas. If you set your Garmin up to use ONLY GPS for speed and distance when you turn it on you can see the speed of the satellite across the sky over you as you show anywhere from .1 to ,25 mph and sometimes higher. This is why you use sensors for speed and distance. The software automatically corrects for the wheel diameter and is more accurate the further the distance is you travel.
>>
>> As for doppler shift - r As you can see that it is not accurate without long term averaging. I worked
on the doppler for bombing control on B52's and while it is useful it
is hardly "very accurate".
>
>Since I was checking my Google mailbox there was Liebermann again being as stupid as humanly possible. What an ass - The B52D was manufactured in 1955 and 1956. I was in the Air Force from 1961 to 1967. Why do you suppose that stupid jackass is talking about GPS when the FIRST satellite wasn't launched until 1973 or so? He has turned into nothing but another copy of Slocum who knows nothing but can use Google like a possum. between the two of them I bet that they can get absolutely anything and everything wrong from the ACTUAL death count from Covid-19 which I showed you the CDC page on Covid-19 death count where there were only 8,000 killed by the illness that is less severe than seasonal flu. Do people die from it? Sure, they ALSO die by the thousands each bad flu year.
>
>There isn't one thing that these dopes could get right if you paid them a million dollars to go to a physicist and ask him to explain it to them. A life of stupidity.

Well, lets see...
Lie number 1 (today)
CDC Covid death count - 8,000 killed
https://covid.cdc.gov/covid-data-tracker/#datatracker-home
Total Deaths
1,049,101

Lie number 2 (Or maybe stupidity #1)
Jeff writes - I worked
on the doppler for bombing control on B52's

Tommy goes rattling on about when he was in the Air Force.

Reality:
The B-52 was equipped with the AN/APN-89 Doppler Ground Speed
Computer.
So it is possible that Jeff did, in fact, work on a "B-52 doppler
system".

So... silly old Tommy falls on his arse once again... right out in
front of everybody

As for Google that Tommy disparages so frequently.

Well, you can't blame him. After all, if you state a "fact" then
Google wants you to post a reference proving that your "fact" is true.
and this presents an insurmountable problem for Tommy, "You want a
reference? But I just told you? You mean you want proof?"
--
Cheers,

John B.

On Thu, 22 Sep 2022 05:49:49 +0700, John B. <slocombjb@gmail.com>
wrote:

>On Wed, 21 Sep 2022 10:08:24 -0700, Jeff Liebermann <jeffl@cruzio.com>
>wrote:
>
>>On Wed, 21 Sep 2022 06:07:25 +0700, John B. <slocombjb@gmail.com>
>>wrote:
>>>A good friend who sails told me that one of his favorite anchorages in
>>>the Philippines is about 100 meters on dry land, according to the GPS.
>>
>>Have your friend check what datum his maps and GPS are using. They
>>should be the same. The default for all GPS receivers is WGS 84. He
>>might be using PRS92 or one of the older datums for the area, such as
>>Luzon 1911. Presumably, he's in one of these 5 zones:
>><https://epsg.io/3121>
>><https://epsg.io/3122>
>><https://epsg.io/3123>
>><https://epsg.io/3124>
>><https://epsg.io/3125>
>>"Modernization of the PHILIPPINE GEODETIC REFERENCE SYSTEM"
>><https://www.namria.gov.ph/jdownloads/Others/StratPlan_Modernization.pdf>

>This was quite a number of years ago but he probably was aware of map
>and GPS datum as this was after he made his first circumnavigation, so
>it wasn't as though he was a novice (:-)

I probably should have been more diplomatic, but I had no way to
determine the expertise of the sailor. I've been in the repair
business long enough to realize that even the most competent person
can sometimes miss the obvious or bungle the basics. I've done both
all too often. So, when someone hands me difficult problem, I always
start with the basics and try to verify any assumptions. I've heard
stories about international sailors missing the Santa Cruz harbor
entrance in the fog because their GPS map was still setup with a datum
from their foreign port of origin. However, those were small errors
of much less than 40 meters (width of the channel at low tide) and not
a relatively huge 100 meter error.
<https://www.santacruzharbor.org/entrance-sounding/>
Still, large datum error are possible:
<https://www.maptools.com/tutorials/map_datum>
"An incorrect datum, can put you hundreds of meters from your actual
position"

So, I resorted to a guess(tm) of what might cause such a large error.
I don't know about the Philippines, but I've seen overlays of old maps
onto a WGS84 modern datum show such larger errors. I really don't
know if it was a datum error, mapping error, survey error, naming
error, human error etc. It's probably too late to determine the cause
today.

Incidentally, some map errors I've seen (and had to deal with) were
errors caused the by the change from older NAD27 datum to the newer
WGS84 datum. (I still run into printed USGS maps that use NAD27).
I'll spare you the details but for many years, the city of Santa Cruz
was misplaced about 50 meters east-west depending on which datum was
in use. About 30(?) years ago, the county put white "X" marks on some
manhole covers and ran aerial photographic surveys. More recently,
LIDAR surveys.
<https://coast.noaa.gov/digitalcoast/data/coastallidar.html>
<https://coast.noaa.gov/dataviewer/#/lidar/search/>
Thanks to modern surveying techniques, my property line is well into
the adjacent property thanks mostly to continental drift, datum
changes and map accuracy errors. Since the survey markers (monuments)
also move with continental drift, it's not much of a problem until we
have an earthquake along one of the local faults:
<https://gis.santacruzcounty.us/DPWScans/recordmaps/089M19.pdf>
I can't find the online database, but each survey marker has an
extensive history. In about 2000, I helped some students find some of
these markers. They discovered that a few had moved thanks to
construction. Oops.

--
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, 22 Sep 2022 06:06:45 +0700, John B. <slocombjb@gmail.com>
wrote:

>On Wed, 21 Sep 2022 14:49:21 -0700, Jeff Liebermann <jeffl@cruzio.com>
>wrote:
>>100% perfect score again. Everything you have to offer is wrong.

>And I'll bet this came as a great surprise?

Yes, this was a surprise, especially since I had previously corrected
two of his amazing facts. Even the most incompetent person usually
guesses correctly some of the time. Even on topics I know nothing
about, I could usually manage to get about 20% correct based on logic
and random guesses. However, Tom consistently scores 100% wrong on so
many diverse topics. The only way he could conceivably be so badly
wrong is to know the right answers, but intentionally provide wrong
answers. I think I understand how he generates consistently wrong
answers, but I fail to understand why. I've always assumed that it
was a good thing to be correct. But, is there some benefit to being
always wrong? Perhaps attracting attention to himself?

--
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, 22 Sep 2022 06:28:44 +0700, John B. <slocombjb@gmail.com>
wrote:
>You might have noticed Tommy mentioning taking a "Carbamazepine"
>tablet. I googled this medication and it is often proscribed for
>"Bipolar disorder" which is described as " a mental health condition
>that affects your moods, which can swing from one extreme to another.
>It used to be known as manic depression" and during the maniac phase
>the following are mentioned as common
>
>talking very quickly
>feeling self-important
>feeling full of great new ideas and having important plans
>being easily distracted
>being easily irritated or agitated
>being delusional, having hallucinations and disturbed or illogical
>thinking

<https://www.nhs.uk/mental-health/conditions/bipolar-disorder/symptoms/>

A friend has bipolar disorder. His entire family is like that, to
varying degrees. He has some of the symptoms listed, but not all of
them. He's been able to moderate the mood swings using drugs and
diet. He's currently a programmer and doing very well working almost
totally at home. One characteristic is that the mood swings occur
fairly rapidly. The longest I've seen him in manic mode was about 12
hrs after which he swung into about an hour of depression. Usually,
the mood swings last 1 to 3 hrs. That's not Tom. He seems to always
be in manic mode, which is hardly bipolar.

--
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, 22 Sep 2022 10:47:42 +0700, John B. <slocombjb@gmail.com>
wrote:

>Lie number 2 (Or maybe stupidity #1)
>Jeff writes - I worked
>on the doppler for bombing control on B52's

Nope. Tom brought up the B52 in a previous tantrum.

<https://groups.google.com/g/rec.bicycles.tech/c/RwWhR9koTg0/m/m7G86fcGAwAJ>
"...As you can see that it is not accurate without long term
averaging. I worked on the Doppler for bombing control on B52's and
while it is useful it is hardly "very accurate"."

Incidentally, there's no connection between Doppler shift and whatever
"long term averaging" might be. Averaging what?

>Tommy goes rattling on about when he was in the Air Force.
>
>Reality:
>The B-52 was equipped with the AN/APN-89 Doppler Ground Speed
>Computer.
>So it is possible that Jeff did, in fact, work on a "B-52 doppler
>system".

Nope, not me. I've worked on non-military avionics, nothing that
might go into a B-52. However, I believe that some of the radars of
the day used Doppler to reduce ground clutter by only displaying
moving objects.
<https://en.wikipedia.org/wiki/Doppler_radar>
(Incidentally, the "history" section story about Dan Rather, Doppler
radar and Hurricane Carla is rather interesting).

--
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, 22 Sep 2022 06:03:22 +0700, John B. <slocombjb@gmail.com>
wrote:

>On Wed, 21 Sep 2022 11:26:10 -0700, Jeff Liebermann <jeffl@cruzio.com>
>wrote:

>>I'm quite familiar with older GPS technology used in farming. The
>>accuracy of such systems is dependent on using differential GPS
>>transmitters located on the ground near the farm. Accuracy is +/- a
>>few centimeters. I have some old AutoFarm hardware that was used for
>>the plowing:
>><https://precisionagricultu.re/autofarm-gps-precision-farming-paradyme/>
>>There's no need for UDR on a farm, where signal obstructions are
>>unlikely. The military has the money to buy all the latest toys. They
>>probably already have UDR GPS receivers. However, UDR won't do
>>anything useful in a missile or airplane, which presumably have the
>>best possible view of the sky.

>I was going to ask you about that as way back when I was involved in
>oil well drilling in West Papua (Irian Jaya) which were located
>referenced to seismic locations that the Seismic guys told us were
>accurate to feet.

Many feet accuracy. When I mumble something about GPS farming, it's
not accuracy that's important. It's resolution. When plowing a
field, nobody cares about the exact location of the property boundary,
which is what accuracy is all about. They care exactly how far apart
and straight are the furrows (trench made by a plow), which requires
resolution and precision. So, a DGPS marker is placed somewhere on
the field, and all measurements are made from the marker. That means
the furrows can be closer together for higher crop yield. Having the
furrows in straight lines is useful for reducing irrigation
requirements and guiding a harvester.

Accuracy, resolution and precision:
<https://www.google.com/search?q=accuracy+resolution+precision>

--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

On Wed, 21 Sep 2022 21:51:06 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

>On Thu, 22 Sep 2022 05:49:49 +0700, John B. <slocombjb@gmail.com>
>wrote:
>
>>On Wed, 21 Sep 2022 10:08:24 -0700, Jeff Liebermann <jeffl@cruzio.com>
>>wrote:
>>
>>>On Wed, 21 Sep 2022 06:07:25 +0700, John B. <slocombjb@gmail.com>
>>>wrote:
>>>>A good friend who sails told me that one of his favorite anchorages in
>>>>the Philippines is about 100 meters on dry land, according to the GPS.
>>>
>>>Have your friend check what datum his maps and GPS are using. They
>>>should be the same. The default for all GPS receivers is WGS 84. He
>>>might be using PRS92 or one of the older datums for the area, such as
>>>Luzon 1911. Presumably, he's in one of these 5 zones:
>>><https://epsg.io/3121>
>>><https://epsg.io/3122>
>>><https://epsg.io/3123>
>>><https://epsg.io/3124>
>>><https://epsg.io/3125>
>>>"Modernization of the PHILIPPINE GEODETIC REFERENCE SYSTEM"
>>><https://www.namria.gov.ph/jdownloads/Others/StratPlan_Modernization.pdf>
>
>>This was quite a number of years ago but he probably was aware of map
>>and GPS datum as this was after he made his first circumnavigation, so
>>it wasn't as though he was a novice (:-)
>
>I probably should have been more diplomatic, but I had no way to
>determine the expertise of the sailor. I've been in the repair
>business long enough to realize that even the most competent person
>can sometimes miss the obvious or bungle the basics. I've done both
>all too often. So, when someone hands me difficult problem, I always
>start with the basics and try to verify any assumptions. I've heard
>stories about international sailors missing the Santa Cruz harbor
>entrance in the fog because their GPS map was still setup with a datum
>from their foreign port of origin. However, those were small errors
>of much less than 40 meters (width of the channel at low tide) and not
>a relatively huge 100 meter error.
><https://www.santacruzharbor.org/entrance-sounding/>
>Still, large datum error are possible:
><https://www.maptools.com/tutorials/map_datum>
>"An incorrect datum, can put you hundreds of meters from your actual
>position"
>
>So, I resorted to a guess(tm) of what might cause such a large error.
>I don't know about the Philippines, but I've seen overlays of old maps
>onto a WGS84 modern datum show such larger errors. I really don't
>know if it was a datum error, mapping error, survey error, naming
>error, human error etc. It's probably too late to determine the cause
>today.
>
>Incidentally, some map errors I've seen (and had to deal with) were
>errors caused the by the change from older NAD27 datum to the newer
>WGS84 datum. (I still run into printed USGS maps that use NAD27).
>I'll spare you the details but for many years, the city of Santa Cruz
>was misplaced about 50 meters east-west depending on which datum was
>in use. About 30(?) years ago, the county put white "X" marks on some
>manhole covers and ran aerial photographic surveys. More recently,
>LIDAR surveys.
><https://coast.noaa.gov/digitalcoast/data/coastallidar.html>
><https://coast.noaa.gov/dataviewer/#/lidar/search/>
>Thanks to modern surveying techniques, my property line is well into
>the adjacent property thanks mostly to continental drift, datum
>changes and map accuracy errors. Since the survey markers (monuments)
>also move with continental drift, it's not much of a problem until we
>have an earthquake along one of the local faults:
><https://gis.santacruzcounty.us/DPWScans/recordmaps/089M19.pdf>
>I can't find the online database, but each survey marker has an
>extensive history. In about 2000, I helped some students find some of
>these markers. They discovered that a few had moved thanks to
>construction. Oops.

I wasn't upset nor probably would my friend have been (:-) But most
who sail in international waters do read the information block on the
chart that they are using. I once came across a chart, in a used chart
shop, of some South Sea Islands marked "Based on the survey made by
the HMS Whatever in 1790". I kept it for quite a while to show people
when discussions of charting came up. I reckoned that if I was
actually using it I'd be a bit cautious about depending on it (:-)
--
Cheers,

John B.

5On Wed, 21 Sep 2022 22:39:00 -0700, Jeff Liebermann
<jeffl@cruzio.com> wrote:

>On Thu, 22 Sep 2022 10:47:42 +0700, John B. <slocombjb@gmail.com>
>wrote:
>
>>Lie number 2 (Or maybe stupidity #1)
>>Jeff writes - I worked
>>on the doppler for bombing control on B52's
>
>Nope. Tom brought up the B52 in a previous tantrum.
>
><https://groups.google.com/g/rec.bicycles.tech/c/RwWhR9koTg0/m/m7G86fcGAwAJ>
>"...As you can see that it is not accurate without long term
>averaging. I worked on the Doppler for bombing control on B52's and
>while it is useful it is hardly "very accurate"."
>
>Incidentally, there's no connection between Doppler shift and whatever
>"long term averaging" might be. Averaging what?
>
>>Tommy goes rattling on about when he was in the Air Force.
>>
>>Reality:
>>The B-52 was equipped with the AN/APN-89 Doppler Ground Speed
>>Computer.
>>So it is possible that Jeff did, in fact, work on a "B-52 doppler
>>system".
>
>Nope, not me. I've worked on non-military avionics, nothing that
>might go into a B-52. However, I believe that some of the radars of
>the day used Doppler to reduce ground clutter by only displaying
>moving objects.
><https://en.wikipedia.org/wiki/Doppler_radar>
>(Incidentally, the "history" section story about Dan Rather, Doppler
>radar and Hurricane Carla is rather interesting).

Re B-52 bombing in Vietnam read
https://www.airforcemag.com/article/0606bombing/
Here is this multi gazillion dollar, super dooper, bomber and they
can't hit the target.

By the way I worked at two of the Thailand bases where the so called
Sky Spot radar systems were sited and they were super secret. Had
their own enclosure, armed guards at the gate and so on. And the
security was effective too. I asked about "what do they do there" and
nobody knew.

--
Cheers,

John B.

On Wednesday, September 21, 2022 at 8:17:20 PM UTC-4, cycl...@gmail.com wrote:
> On Wednesday, September 21, 2022 at 2:09:22 PM UTC-7, Tom Kunich wrote:

> >
> > As for doppler shift - https://www.researchgate.net/figure/Doppler-Shift-Prediction-Accuracy_fig2_352548023 As you can see that it is not accurate without long term averaging. I worked on the doppler for bombing control on B52's and while it is useful it is hardly "very accurate".
> Since I was checking my Google mailbox there was Liebermann again being as stupid as humanly possible. What an ass - The B52D was manufactured in 1955 and 1956.

Attempt at distraction duly noted. No one mentioned anything about any specific model of B52. Besides that, the D variant was released in december of 1956, so you're wrong about that too.

> I was in the Air Force from 1961 to 1967. Why do you suppose that stupid jackass is talking about GPS when the FIRST satellite wasn't launched until 1973 or so?

Because this conversation is about GPS, not doppler radar. You for some inexplicable reason brought up doppler radar in a conversation about GPS. Your work (?) on doppler radar has absolutely nothing to do with a conversation on GPS. Why did _you_ bring up doppler radar in a discussion about CPS, you stupid jackass?

> He has turned into nothing but another copy of Slocum who knows nothing but can use Google like a possum.

Possums can use google? That makes them one step ahead of you.

> between the two of them I bet that they can get absolutely anything and everything wrong from the
> ACTUAL death count from Covid-19 which I showed you the CDC page on Covid-19 death count where
> there were only 8,000 killed by the illness that is less severe than seasonal flu. Do people die from it?
> Sure, they ALSO die by the thousands each bad flu year.

This again...Give it up, sparky. We've shown repeatedly how you intentionally misread the CDC data. You're lying, and we all know it.

> There isn't one thing that these dopes could get right if you paid them a million dollars to go to a physicist and ask him to explain it to them. A life of stupidity.

Find us a physicist who agrees that PWM is used to test cables.
Shut the fuck up, tommy

On Thu, 22 Sep 2022 04:57:47 -0700 (PDT), "funkma...@hotmail.com"
<funkmasterxx@hotmail.com> wrote:

>Because this conversation is about GPS, not doppler radar. You for some inexplicable reason brought up doppler radar in a conversation about GPS. Your work (?) on doppler radar has absolutely nothing to do with a conversation on GPS. Why did _you_ bring up doppler radar in a discussion about CPS, you stupid jackass?

Umm... that was my fault. I mentioned that GPS speed is measured by
using Doppler shift, not by dividing distance between positions by
time. Doppler is more accurate because there are no errors produced
by atmospheric diffraction. Tom used that as a launch platform to
switch topic from bicycle riding speeds to B52.

>Find us a physicist who agrees that PWM is used to test cables.
>Shut the fuck up, tommy

I want to see some of his rides appear on Strava. Until I see real
results that match his descriptions, I don't believe any of his
descriptions.

Gone for another walk in the park. Hopefully two hours of trudging
and discussing politics.
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

On Thursday, September 22, 2022 at 10:43:10 AM UTC-4, jeff.li...@gmail.com wrote:
> On Thu, 22 Sep 2022 04:57:47 -0700 (PDT), "funkma...@hotmail.com"
> <funkma...@hotmail.com> wrote:
>
> >Because this conversation is about GPS, not doppler radar. You for some inexplicable reason brought up doppler radar in a conversation about GPS. Your work (?) on doppler radar has absolutely nothing to do with a conversation on GPS. Why did _you_ bring up doppler radar in a discussion about CPS, you stupid jackass?
> Umm... that was my fault. I mentioned that GPS speed is measured by
> using Doppler shift, not by dividing distance between positions by
> time.

Not to my understanding. Doppler shift is the compression/expansion of the frequency from a known source in reference to a known receiver. GPS is fundamentally a positioning tool - triangulation from timestamps versus arrival time on the receiver. This is shown by the NMEA string of the receiver output. That isn't doppler shift, in fact, doppler shift could corrupt the GPS data if it forces the carrier frequency to shift outside the limits of the receiver.. The speed calculated from GPS is a function of the distance traveled between established positions over time.

> Doppler is more accurate because there are no errors produced
> by atmospheric diffraction.

Not sure what that means. The receiver must lock onto the various satellites carrier frequencies to extract the timestamp data. Doppler shift may be compensated for in the receiver (knowing the Fr shift as a function of the direction traveled) but I'm pretty sure doppler isn't used as part of the positioning or speed calculations.

On Thu, 22 Sep 2022 12:05:31 -0700 (PDT), "funkma...@hotmail.com"
<funkmasterxx@hotmail.com> wrote:

>On Thursday, September 22, 2022 at 10:43:10 AM UTC-4, jeff.li...@gmail.com wrote:
>> On Thu, 22 Sep 2022 04:57:47 -0700 (PDT), "funkma...@hotmail.com"
>> <funkma...@hotmail.com> wrote:
>>
>> >Because this conversation is about GPS, not doppler radar. You for some inexplicable reason brought up doppler radar in a conversation about GPS. Your work (?) on doppler radar has absolutely nothing to do with a conversation on GPS. Why did _you_ bring up doppler radar in a discussion about CPS, you stupid jackass?
>> Umm... that was my fault. I mentioned that GPS speed is measured by
>> using Doppler shift, not by dividing distance between positions by
>> time.
>
>Not to my understanding. Doppler shift is the compression/expansion of the frequency from a known source in reference to a known receiver. GPS is fundamentally a positioning tool - triangulation from timestamps versus arrival time on the receiver. This is shown by the NMEA string of the receiver output. That isn't doppler shift, in fact, doppler shift could corrupt the GPS data if it forces the carrier frequency to shift outside the limits of the receiver.. The speed calculated from GPS is a function of the distance traveled between established positions over time.
>
>> Doppler is more accurate because there are no errors produced
>> by atmospheric diffraction.
>
>Not sure what that means. The receiver must lock onto the various satellites carrier frequencies to extract the timestamp data. Doppler shift may be compensated for in the receiver (knowing the Fr shift as a function of the direction traveled) but I'm pretty sure doppler isn't used as part of the positioning or speed calculations.

"GPS Speedometer Principle of speed measurement using GPS"
<https://www.onosokki.co.jp/English/hp_e/products/keisoku/automotive/lc8_principle.htm>

"The Ionospheric Effect"
<https://www.e-education.psu.edu/geog862/node/1715>
"One of the largest errors in GPS positioning is attributable to the
atmosphere."

"Doppler GPS speed and heading"
<https://forums.garmin.com/developer/connect-iq/f/discussion/7609/doppler-gps-speed-and-heading>

"How does a GNSS receiver estimate velocity?"
<https://insidegnss.com/how-does-a-gnss-receiver-estimate-velocity/>
"Improved performance could be achieved by processing differences of
consecutive carrier phase measurements (TDCP – time-differenced
carrier phase), a strategy that enables velocity accuracies one order
of magnitude better than the “raw” Doppler measurements output from
the receiver’s tracking loops."

I'm not sure about this one, but this GPS bicycle speedometer outputs
only altitude, speed and time, which it uses to calculate distance.
<https://www.amazon.com/MEILAN-Computer-Wireless-Speedometer-Waterproof/dp/B07SM5QLW3/>
No position (lat-long) output. The chip might be capable of producing
lat-long and using that and the clock to calculate speed, but it
(probably) doesn't and instead just displays Doppler speed.

More later...

--
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, 22 Sep 2022 16:45:51 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

>On Thu, 22 Sep 2022 12:05:31 -0700 (PDT), "funkma...@hotmail.com"
><funkmasterxx@hotmail.com> wrote:
>
>>On Thursday, September 22, 2022 at 10:43:10 AM UTC-4, jeff.li...@gmail.com wrote:
>>> On Thu, 22 Sep 2022 04:57:47 -0700 (PDT), "funkma...@hotmail.com"
>>> <funkma...@hotmail.com> wrote:
>>>
>>> >Because this conversation is about GPS, not doppler radar. You for some inexplicable reason brought up doppler radar in a conversation about GPS. Your work (?) on doppler radar has absolutely nothing to do with a conversation on GPS. Why did _you_ bring up doppler radar in a discussion about CPS, you stupid jackass?
>>> Umm... that was my fault. I mentioned that GPS speed is measured by
>>> using Doppler shift, not by dividing distance between positions by
>>> time.
>>
>>Not to my understanding. Doppler shift is the compression/expansion of the frequency from a known source in reference to a known receiver. GPS is fundamentally a positioning tool - triangulation from timestamps versus arrival time on the receiver. This is shown by the NMEA string of the receiver output. That isn't doppler shift, in fact, doppler shift could corrupt the GPS data if it forces the carrier frequency to shift outside the limits of the receiver.. The speed calculated from GPS is a function of the distance traveled between established positions over time.
>>
>>> Doppler is more accurate because there are no errors produced
>>> by atmospheric diffraction.
>>
>>Not sure what that means. The receiver must lock onto the various satellites carrier frequencies to extract the timestamp data. Doppler shift may be compensated for in the receiver (knowing the Fr shift as a function of the direction traveled) but I'm pretty sure doppler isn't used as part of the positioning or speed calculations.
>
>"GPS Speedometer Principle of speed measurement using GPS"
><https://www.onosokki.co.jp/English/hp_e/products/keisoku/automotive/lc8_principle.htm>
>
>"The Ionospheric Effect"
><https://www.e-education.psu.edu/geog862/node/1715>
>"One of the largest errors in GPS positioning is attributable to the
>atmosphere."
>
>"Doppler GPS speed and heading"
><https://forums.garmin.com/developer/connect-iq/f/discussion/7609/doppler-gps-speed-and-heading>
>
>"How does a GNSS receiver estimate velocity?"
><https://insidegnss.com/how-does-a-gnss-receiver-estimate-velocity/>
>"Improved performance could be achieved by processing differences of
>consecutive carrier phase measurements (TDCP – time-differenced
>carrier phase), a strategy that enables velocity accuracies one order
>of magnitude better than the “raw” Doppler measurements output from
>the receiver’s tracking loops."
>
>I'm not sure about this one, but this GPS bicycle speedometer outputs
>only altitude, speed and time, which it uses to calculate distance.
><https://www.amazon.com/MEILAN-Computer-Wireless-Speedometer-Waterproof/dp/B07SM5QLW3/>
>No position (lat-long) output. The chip might be capable of producing
>lat-long and using that and the clock to calculate speed, but it
>(probably) doesn't and instead just displays Doppler speed.
>
>More later...

I don't know about the bicycle meters but my walking meter (Simply
Walking) has the ability to show a map and your location on the map as
you walk. I had always assumed that was how distance and speed was
calculated.
--
Cheers,

John B.

On Fri, 23 Sep 2022 06:56:18 +0700, John B. <slocombjb@gmail.com>
wrote:

>On Thu, 22 Sep 2022 16:45:51 -0700, Jeff Liebermann <jeffl@cruzio.com>
>wrote:
>
>>On Thu, 22 Sep 2022 12:05:31 -0700 (PDT), "funkma...@hotmail.com"
>><funkmasterxx@hotmail.com> wrote:
>>
>>>On Thursday, September 22, 2022 at 10:43:10 AM UTC-4, jeff.li...@gmail.com wrote:
>>>> On Thu, 22 Sep 2022 04:57:47 -0700 (PDT), "funkma...@hotmail.com"
>>>> <funkma...@hotmail.com> wrote:
>>>>
>>>> >Because this conversation is about GPS, not doppler radar. You for some inexplicable reason brought up doppler radar in a conversation about GPS. Your work (?) on doppler radar has absolutely nothing to do with a conversation on GPS. Why did _you_ bring up doppler radar in a discussion about CPS, you stupid jackass?
>>>> Umm... that was my fault. I mentioned that GPS speed is measured by
>>>> using Doppler shift, not by dividing distance between positions by
>>>> time.
>>>
>>>Not to my understanding. Doppler shift is the compression/expansion of the frequency from a known source in reference to a known receiver. GPS is fundamentally a positioning tool - triangulation from timestamps versus arrival time on the receiver. This is shown by the NMEA string of the receiver output. That isn't doppler shift, in fact, doppler shift could corrupt the GPS data if it forces the carrier frequency to shift outside the limits of the receiver.. The speed calculated from GPS is a function of the distance traveled between established positions over time.
>>>
>>>> Doppler is more accurate because there are no errors produced
>>>> by atmospheric diffraction.
>>>
>>>Not sure what that means. The receiver must lock onto the various satellites carrier frequencies to extract the timestamp data. Doppler shift may be compensated for in the receiver (knowing the Fr shift as a function of the direction traveled) but I'm pretty sure doppler isn't used as part of the positioning or speed calculations.
>>
>>"GPS Speedometer Principle of speed measurement using GPS"
>><https://www.onosokki.co.jp/English/hp_e/products/keisoku/automotive/lc8_principle.htm>
>>
>>"The Ionospheric Effect"
>><https://www.e-education.psu.edu/geog862/node/1715>
>>"One of the largest errors in GPS positioning is attributable to the
>>atmosphere."
>>
>>"Doppler GPS speed and heading"
>><https://forums.garmin.com/developer/connect-iq/f/discussion/7609/doppler-gps-speed-and-heading>
>>
>>"How does a GNSS receiver estimate velocity?"
>><https://insidegnss.com/how-does-a-gnss-receiver-estimate-velocity/>
>>"Improved performance could be achieved by processing differences of
>>consecutive carrier phase measurements (TDCP – time-differenced
>>carrier phase), a strategy that enables velocity accuracies one order
>>of magnitude better than the “raw” Doppler measurements output from
>>the receiver’s tracking loops."
>>
>>I'm not sure about this one, but this GPS bicycle speedometer outputs
>>only altitude, speed and time, which it uses to calculate distance.
>><https://www.amazon.com/MEILAN-Computer-Wireless-Speedometer-Waterproof/dp/B07SM5QLW3/>
>>No position (lat-long) output. The chip might be capable of producing
>>lat-long and using that and the clock to calculate speed, but it
>>(probably) doesn't and instead just displays Doppler speed.
>>
>>More later...

>I don't know about the bicycle meters but my walking meter (Simply
>Walking) has the ability to show a map and your location on the map as
>you walk. I had always assumed that was how distance and speed was
>calculated.

"Assumption, the mother of all screwups". I hate to admit it, but I
made the same assumption for many years after GPS Doppler speed
measurement was introduced. I was duly notified of my error in
sci.geo.satellite-nav newsgroup.

"Development of an Electronic Speed Measurement System for Evaluating
the Accuracy of GNSS Receivers and Statistical Analysis of Their
Performance in Speed Measurements"
<https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.1058.3601&rep=rep1&type=pdf>
See Section 2.2 for some history of how we got here:

"The early days GPS receivers used distance over time based method for
speed determination. As distance between neighboring two position
records can be calculated by the receiver and time between such
records is known, it is possible to calculate speed. This method is
inaccurate because it depends on positional accuracy, frequency of
positional measurements and curvature of the road."

"The next generation of receivers started to use the so
called Doppler based methodologies for speed determination.
They might be split into raw Doppler method and method
based on Carrier Phase observations..."

Note that there is some discussion on "outliers" which are data points
that deviate radically from normal data. See section 4.2. Such very
high speeds and "outliers" are probably what several people observed
on their Garmin maximum speed records.

"Medium range and low grade GPS receivers generated relatively
substantial number of measurement outliers around overpasses with up
to 10 km/h reported errors in speed measurements. In addition, the
medium range receiver generated relatively high numbers of outliers in
the areas where tree canopies surround some sections of the road."

In other words, some GPS receivers (or firmware) are junk.

Also, if you search the document for "Doppler", you'll find that speed
measurement is heavily tied to Doppler shift measurement.

--
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, 22 Sep 2022 21:50:08 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

>On Fri, 23 Sep 2022 06:56:18 +0700, John B. <slocombjb@gmail.com>
>wrote:
>
>>On Thu, 22 Sep 2022 16:45:51 -0700, Jeff Liebermann <jeffl@cruzio.com>
>>wrote:
>>
>>>On Thu, 22 Sep 2022 12:05:31 -0700 (PDT), "funkma...@hotmail.com"
>>><funkmasterxx@hotmail.com> wrote:
>>>
>>>>On Thursday, September 22, 2022 at 10:43:10 AM UTC-4, jeff.li...@gmail.com wrote:
>>>>> On Thu, 22 Sep 2022 04:57:47 -0700 (PDT), "funkma...@hotmail.com"
>>>>> <funkma...@hotmail.com> wrote:
>>>>>
>>>>> >Because this conversation is about GPS, not doppler radar. You for some inexplicable reason brought up doppler radar in a conversation about GPS. Your work (?) on doppler radar has absolutely nothing to do with a conversation on GPS. Why did _you_ bring up doppler radar in a discussion about CPS, you stupid jackass?
>>>>> Umm... that was my fault. I mentioned that GPS speed is measured by
>>>>> using Doppler shift, not by dividing distance between positions by
>>>>> time.
>>>>
>>>>Not to my understanding. Doppler shift is the compression/expansion of the frequency from a known source in reference to a known receiver. GPS is fundamentally a positioning tool - triangulation from timestamps versus arrival time on the receiver. This is shown by the NMEA string of the receiver output. That isn't doppler shift, in fact, doppler shift could corrupt the GPS data if it forces the carrier frequency to shift outside the limits of the receiver.. The speed calculated from GPS is a function of the distance traveled between established positions over time.
>>>>
>>>>> Doppler is more accurate because there are no errors produced
>>>>> by atmospheric diffraction.
>>>>
>>>>Not sure what that means. The receiver must lock onto the various satellites carrier frequencies to extract the timestamp data. Doppler shift may be compensated for in the receiver (knowing the Fr shift as a function of the direction traveled) but I'm pretty sure doppler isn't used as part of the positioning or speed calculations.
>>>
>>>"GPS Speedometer Principle of speed measurement using GPS"
>>><https://www.onosokki.co.jp/English/hp_e/products/keisoku/automotive/lc8_principle.htm>
>>>
>>>"The Ionospheric Effect"
>>><https://www.e-education.psu.edu/geog862/node/1715>
>>>"One of the largest errors in GPS positioning is attributable to the
>>>atmosphere."
>>>
>>>"Doppler GPS speed and heading"
>>><https://forums.garmin.com/developer/connect-iq/f/discussion/7609/doppler-gps-speed-and-heading>
>>>
>>>"How does a GNSS receiver estimate velocity?"
>>><https://insidegnss.com/how-does-a-gnss-receiver-estimate-velocity/>
>>>"Improved performance could be achieved by processing differences of
>>>consecutive carrier phase measurements (TDCP – time-differenced
>>>carrier phase), a strategy that enables velocity accuracies one order
>>>of magnitude better than the “raw” Doppler measurements output from
>>>the receiver’s tracking loops."
>>>
>>>I'm not sure about this one, but this GPS bicycle speedometer outputs
>>>only altitude, speed and time, which it uses to calculate distance.
>>><https://www.amazon.com/MEILAN-Computer-Wireless-Speedometer-Waterproof/dp/B07SM5QLW3/>
>>>No position (lat-long) output. The chip might be capable of producing
>>>lat-long and using that and the clock to calculate speed, but it
>>>(probably) doesn't and instead just displays Doppler speed.
>>>
>>>More later...
>
>>I don't know about the bicycle meters but my walking meter (Simply
>>Walking) has the ability to show a map and your location on the map as
>>you walk. I had always assumed that was how distance and speed was
>>calculated.
>
>"Assumption, the mother of all screwups". I hate to admit it, but I
>made the same assumption for many years after GPS Doppler speed
>measurement was introduced. I was duly notified of my error in
>sci.geo.satellite-nav newsgroup.

Well (:-) When making an open ocean trip, on a sail boat, one
calculates the speed by marking up the position for the "Noon Fix"
and measuring the distance from the last "Noon Fix" and dividing by 24
(:-)

--
Cheers,

John B.

On Fri, 23 Sep 2022 12:39:05 +0700, John B. <slocombjb@gmail.com>
wrote:

>Well (:-) When making an open ocean trip, on a sail boat, one
>calculates the speed by marking up the position for the "Noon Fix"
>and measuring the distance from the last "Noon Fix" and dividing by 24
>(:-)

Nope. The navigator throws a floating "chip log" overboard, with a
knotted rope attached. The rope knots are spaced 17 ft apart. The
navigator counts how many knots go through his hands in 10 seconds. If
5 knots pass through the navigators hands in 10 seconds, the vessel
speed is 5 knots. If you want mph, a speed of 1 knot equals about
1.15 mph. One could probably do this on a bicycle, but I don't think
it would be very accurate (or easy).

Noon sights will work, but it's easier to just read the speed off the
GPS display.

About 20 years ago, I showed a group of high skool students how a
sextant was used to calculate longitude. Most could not believe that
sailors went through all the calculations and that navigators used
sight reduction tables (HO 229), plotting tables, and "drafting"
instruments. The consensus was that it was "too complicated to be
useful". Sigh.

--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558