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Old 06-24-13, 03:35 PM   #1
oaklane2
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Android phone for Strava

I am trying to use my Moto Razr HD to track my rides with Strava. The phone ends up cutting me across country and never gives me the same route on my circuit rides and cuts anywhere from .25 to two miles off the total compared to my bike computer. Is it normal for this to happen? The only issue that I can see with my use is I have the phone in a ziplock bag (to protect it from sweat) inside a cinch bag.

Does anyone else have issues with tracking rides with a phone?
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Old 06-24-13, 04:17 PM   #2
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Nope, although milage will be a bit off as its useong GPS and it depends on how many SATs u have and also the accuracy of the phone?

I find mine can vary 0.1-0.5 of a mile over a 15-20 mile rode but never 2 miles but I only use it for tracking, if opi want truly acuret distance I ipuse cyclo computer.

Don't forget it depends how often the GPS signal is being updated so if its not very often and our at high speed you cover more ground over same update so it dress alone and measures the distance bewptween the two measured points to get distance dome.

If u zoom in on the map of your ride u can see what I mean and how the line is actual a serious a straight lines jhioned up and never curved, so its no a continues signal on GPS its more like on of.


So it doesn't know were u are exactly all the time and this can add up over time?

That's my theory anyways?

So its king of like if the time between signals was say a minute of you went in a straight line the distance would be acuret but u went back and forward I then measures the distance bewtween were u are now and were u were as it doesn't know you have been backward and do reward of that makes any sense?

Although itmdosent take a minuet its more like it updates every second or a few times every second?

Its hard to explain but I know what I mean haha BH it its only a theory.

Also don't forget were you actually are and were GPS thinks you are can be different as its not mill sped GPS which is much more acuret this is only what us public have access to, so again data could be lost there

So between the two I expect it to be out a tiny bit but not 2 hole miles.


Then again I could be compleatly wrong.

But its mind of like resoution think, think of video quality a HD video is easier to watch and understand what is happing compered to VGA quality ...kinda.


OK lll stop rambling now,
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Old 06-24-13, 05:01 PM   #3
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The GPS is takes positions periodically. That means the GPS track is going to be straight-line segments between each position it records. Plus, there's some error (inaccuracies) in the GPS position data.

The wheel sensor, on the other hand is much more accurate for distance travelled. The GPS and the wheel sensor distance should be very close the more your actual riding path is a straight line (or made-up of relatively long straight line segments).

GPS will also be more accurate for higher rates of speed (much higher than you will typically be riding at).

GPS will often register a small speed when you are standing still. That's the error (position inaccuracies) telling the GPS that you are "moving".

A dedicated GPS unit might give better results than the one in the phone too.

Last edited by njkayaker; 06-24-13 at 05:04 PM.
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Old 06-24-13, 07:19 PM   #4
oaklane2
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Thanks all. I understand the GPS inaccuracies, just was shocked at lack of updates for sometimes a mile at a time when I had made a turn and it has me cutting across a field and river lol. Thinking of upgrading to a dedicated GPS if they are more accurate. Mostly I was curious if having an android in a ziplock bag inside a cinch bag on my back was maybe causing some inaccuracy. Thanks again.
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Old 06-24-13, 08:52 PM   #5
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Are you sure you are using GPS and not AGPS? Because what your are describing is how AGPS would work. I have zero problems with my retired HTC Incredible (no data, no cell connection). Look how it traces my rides: http://app.strava.com/activities/56712305
What do you have checked in settings->location?
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Old 06-25-13, 05:13 PM   #6
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Could it have something to do with a poor connection to your cell network? I confess to not knowing how Strava works but I'm guessing it uses GPS for location and the cell network for map info and calculating your speed/rank on segments. It's possible the tracking doesn't work well when the cell signal is weak.
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Old 06-25-13, 05:23 PM   #7
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Quote:
Originally Posted by Dunbar View Post
Could it have something to do with a poor connection to your cell network? I confess to not knowing how Strava works but I'm guessing it uses GPS for location and the cell network for map info and calculating your speed/rank on segments. It's possible the tracking doesn't work well when the cell signal is weak.
It has nothing to do with the cell-network. It doesn't need the cell-network.

Tracking just entails collecting position/location and time data using the gps. That data actually has nothing to do with maps. It's pure lat/long and time data.
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