Accuracy problems on iPhone

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Accuracy problems on iPhone

Postby wlk on Mon Jul 11, 2011 10:46 am

I'm using Pro version on iPhone 4 and found out strange problems while hiking in mountains. When I get to places, where it is hard to get good GPS reception (ie valley in mountains and so on), accuracy of logged points is sometimes way out. I understand, that iPhone is supposed to provide accuracy level of given GPS coordinates. But is seems to me, that its sometimes providing wrong coords (up to few hundreds meters away from current position) with good accuracy info, so it is saved to my log.

When I check my trips on map, there are some points way out of trail and speed value on graph goes way out of possible walking speed. Unfortunately I already cleaned worst parts in this http://www.everytrail.com/view_trip.php?trip_id=1183567 trip, but there are still some strange parts.

EDIT One is between 3:26:42 and 3:30:25 - there should be straight line, but app logged strange circuity ending at 3:28:10. Strange thing is that there are more points logged with this inaccuracy, creating fake trail recognizable just by extreme speed (46kmph) and knowledge, that there is no such path there..

Is there any chance to avoid this errors? Maybe including some profiles for hiking/cycling/driving with speed filters and checks?

I have been using other app on iphone to track my trips (Trails), which is much more prone to these errors (check this funny log http://www.everytrail.com/view_trip.php?trip_id=1183737). I replaced it with EveryTrail, which is much better, but still logs errors and anomalies.
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Re: Accuracy problems on iPhone

Postby chris on Mon Jul 18, 2011 11:41 am

The app can only log the data that it receives from the iPhone, which is sometimes not great in the mountains because the signal can bounce off of mountains / cliffs and give them impression that you are somewhere else. I think the only way to correct this is to go the edit map page and manually move the erroneous points.
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Re: Accuracy problems on iPhone

Postby wlk on Mon Jul 18, 2011 10:53 pm

And is there some correcting mechanism in ET app - like averaging more coords or check for time/distance travelled? It could help a lot...
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