Fitness GPS Accuracy

[boster]

There are a few forums I might choose for this question. Please forgive (or advise) if I've chosen the wrong one.

I have a Samsung Galaxy S5. Love it. My daughter has an iPhone 6. She loves it.

My daughter and I were running together on a track around a park. I had Samsung's S Health app running to track my time and distance. She had two different apps on her iPhone doing the same (Fitbit and Under Armor apps).

One lap around the track came out this way:

1. iPhone/Under Armor: 0.75 miles
2. iPhone/Fitbit: 0.72 miles
3. Samsung/S Health: 0.66 miles

I was surprised at the differences (especially the difference between the two apps running on the same iPhone).

After 3 laps our apps reported notably different distances run. Her Under Armor app said we'd run 2.5 miles, while my S Health app said we'd run 2.0 miles. Since they reported the same time we were running, they reported very different paces. This is annoying because she and I are trying to reach a certain pace in preparation for a half-marathon.

This question really isn't about fitness. It's about the accuracy of GPS and the tools which read the GPS data.

Is there a way (without putting on a white lab coat and running thousands of double-blind studies, etc.) to figure out why the devices/apps reported such different values?

On my phone, S Health is allowed all the permissions is asks for, including Location. I know location accuracy depends on the technology being used, and I have my phone's location mode set to High Accuracy.

-boster

 

[AZgl1500]

the GPS on both devices is equally accurate for the most part.

what is different is the timing between GPS fixes... and all 3 of those apps will draw a line between the Marker points at the time the GPS fix was acquired.

there are several good GPS map programs that are intended for folks who walk, traipse thru the woods, etc.... they take a fix ever minute or two... that gives you a much tighter cookie crumb trail on your exact walking path.

I have one called CoPilot USA that has a Walking Mode but there are others that are much better for what you want.

here are a few of them

https://play.google.com/store/searc...WFwIG15IHdhbGt6BRgAwAECigECCAE=:S:ANO1ljLSIq8

 

[AZgl1500]

* CoPilot GPS - Plan & explore! - Android Apps on Google Play

has a walking mode, it also has the single best list of local listings of attractions, etc... of any app, or car gps.

if you use this one, make darn sure you set the Default map storage to extSDcard... otherwise, you phone's internal storage will take a BIG hit.

and, for your use, download only the local region or state, not the whole of the USA. that is huge!!!

 

[steiny180]

The measurement accuracy depends on three things.

1. The GPS sampling rate of your position by each app,
2. The (non)straightness of the path of your route, and
3. The weather and canopy.

The faster the sampling rate, the more accurate your measurements will be, especially in a non-straight path.

If your route is a straight line, then the sampling rate problem is minimized.

If there's foul weather and/or a heavy canopy, the GPS signal may be intermittently blocked, resulting in a slower sampling rate and lower accuracy.

 

[boster]

Thank you all. I'll give other apps a try.