Feelgoodranch
New Member
How accurate are bike phone apps utilizing GPS mileage tracking compared to mileage noted on bike computer properly calibrated?
Accuracy
- Thread starter Feelgoodranch
- Start date
fooferdoggie
Well-Known Member
my iphone is ok but does not agree with my garmin bike computer. I ran stravia and the apple watch bike app and they did not match. my garmin watch and computer are pretty close. the bike computer depends on tire size. I diled in one of my bosch powered bikes now the averages are around .10% or so with the gamin.
Feelgoodranch
New Member
Thanks. This is my reason for posting. I calibrated my Bosch Intuvia using tire circumference (measured) and not close to iPhone Ride my GPS
Feelgoodranch
New Member
not close to my IPhone Ride With GPS app. It appears GPS accuracy not that accurate for trip mileage calculations.
fooferdoggie
Well-Known Member
think the phone is not as accurate. my two garmins are pretty close. you cant use mph the gps jumps around too much. use the average speed. here are mine and my wifes garmin . watches I think she forgot to pause hers so it may have a few more blips but pretty close.
Mr. Coffee
Well-Known Member
- Region
- USA
- City
- A Demented Corner of the North Cascades
There are fairly hairy mathematical reasons distance and speed computed by GPS are almost always high:
spectrum.ieee.org
The above link should be titled: "why every gps overestimates distance traveled".
www.ncbi.nlm.nih.gov
Although my Bosch-Intuvia equipped bike seems to be about 2% higher than my Garmin GPS. Go figure.
Why Every GPS Overestimates Distance Traveled
Math proves that GPS distance, on average, exceeds the actual distance traveled
spectrum.ieee.org
The above link should be titled: "why every gps overestimates distance traveled".
Why GPS makes distances bigger than they are - PMC
Global navigation satellite systems such as the Global Positioning System (GPS) is one of the most important sensors for movement analysis. GPS is widely used to record the trajectories of vehicles, animals and human beings. However, all GPS ...
www.ncbi.nlm.nih.gov
Although my Bosch-Intuvia equipped bike seems to be about 2% higher than my Garmin GPS. Go figure.
fooferdoggie
Well-Known Member
I think Bosch fudges the numbers a bit. seems all the garmins and phones I have used and two bosh bikes on purion one intuvia both bikes seem a mile to 1.5 miles faster then the garmins and phones show.There are fairly hairy mathematical reasons distance and speed computed by GPS are almost always high:
Why Every GPS Overestimates Distance Traveled
Math proves that GPS distance, on average, exceeds the actual distance traveled
The above link should be titled: "why every gps overestimates distance traveled".
Why GPS makes distances bigger than they are - PMC
Global navigation satellite systems such as the Global Positioning System (GPS) is one of the most important sensors for movement analysis. GPS is widely used to record the trajectories of vehicles, animals and human beings. However, all GPS ...
Although my Bosch-Intuvia equipped bike seems to be about 2% higher than my Garmin GPS. Go figure.
Feelgoodranch
New Member
There are fairly hairy mathematical reasons distance and speed computed by GPS are almost always high:
Why Every GPS Overestimates Distance Traveled
Math proves that GPS distance, on average, exceeds the actual distance traveled
The above link should be titled: "why every gps overestimates distance traveled".
Why GPS makes distances bigger than they are - PMC
Global navigation satellite systems such as the Global Positioning System (GPS) is one of the most important sensors for movement analysis. GPS is widely used to record the trajectories of vehicles, animals and human beings. However, all GPS ...
Although my Bosch-Intuvia equipped bike seems to be about 2% higher than my Garmin GPS. Go figure.
Feelgoodranch
New Member
Not to belabor or “overthink” this post which I made out of curiosity; there is some irony realized when GPS guided smart bombs reportedly accurate to inches launched from long distances...you think? Am I missing something?
BrianK
Well-Known Member
- Region
- USA
- City
- NOVA
The ability of GPS accuracy to measure down to inches is limited to military use. Civilians cannot access that accuracy. They can only measure down to a certain number of yards, not inches, so the “enemy” doesn’t use our domestic GPS against us.
Or at least that’s what I read a number of years ago.
Feelgoodranch
New Member
Current information from Google, FWIW.
Is military GPS more accurate than civilian GPS?
The user range error (URE) of the GPS signals in space is actually the same for the civilian and military GPS services. However, most of today's civilian devices use only one GPS frequency, while military receivers use two.
Using two GPS frequencies improves accuracy by correcting signal distortions caused by Earth's atmosphere. Dual-frequency GPS equipment is commercially available for civilian use, but its cost and size has limited it to professional applications.
With augmentation systems, civilian users can actually receive better GPS accuracy than the military. LEARN MORE
Doesn't the government degrade civilian GPS accuracy?
No. During the 1990s, GPS employed a feature called Selective Availability that intentionally degraded civilian accuracy on a global basis.
In May 2000, at the direction of President Bill Clinton, the U.S. government ended its use of Selective Availability in order to make GPS more responsive to civil and commercial users worldwide.
The United States has no intent to ever use Selective Availability again. LEARN MORE
Is military GPS more accurate than civilian GPS?
The user range error (URE) of the GPS signals in space is actually the same for the civilian and military GPS services. However, most of today's civilian devices use only one GPS frequency, while military receivers use two.
Using two GPS frequencies improves accuracy by correcting signal distortions caused by Earth's atmosphere. Dual-frequency GPS equipment is commercially available for civilian use, but its cost and size has limited it to professional applications.
With augmentation systems, civilian users can actually receive better GPS accuracy than the military. LEARN MORE
Doesn't the government degrade civilian GPS accuracy?
No. During the 1990s, GPS employed a feature called Selective Availability that intentionally degraded civilian accuracy on a global basis.
In May 2000, at the direction of President Bill Clinton, the U.S. government ended its use of Selective Availability in order to make GPS more responsive to civil and commercial users worldwide.
The United States has no intent to ever use Selective Availability again. LEARN MORE
Mr. Coffee
Well-Known Member
- Region
- USA
- City
- A Demented Corner of the North Cascades
Let's say you are riding at 20fps, or around 13.6 mph. That is a comfortable pace and makes things easy to understand.
20fps is 240 inches per second. And a 2.4 inch error could easily translate into a 1% error in speed if you sampled once per second. You'd think the sample errors would cancel out but if you dig into the mathematics they generally do not. if you dig deeper into the mathematics you find that the error is almost always high.
Also paradoxically a higher sample rate doesn't necessarily lead to lower errors.
There are fancier ways to calculate speed and distance using GPS, but they generally require fancier (read: much more expensive) receivers and aren't commonly used in end-user applications.
fooferdoggie
Well-Known Member
my wife and I on our tandem her in back both of us with the same garmin watch. one segment in stravia she was realty fast. one second faster then me (G)
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