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I'm not sure if this is an issue with the gps, the app I'm using, or android itself, but since it's android that ties it altogether, I'll try posting this here (let me know if I should move this to a better spot).

I tend to use my phone's (Samsung galaxy S2) gps along with MyTracks app to record when I go on a hike. Mostly it works fine, but every once in a while, I get this strange result: Raw path

Obviously, I can't hike this path in a few hours, so something is definitely wrong with the resulting coordinates. I write a quick script to filter out anything that looks too far (anything more then a few degrees difference), eliminating those far off points. I get this: Some points cleaned

I try to filter it some more by tightening my error values or random things that come to mind, but it doesn't really work well. I did notice though that all was not lost as it actually recorded the first half just fine and the actual path looks like this: Actual Path

But the added return path looks like this: Added return path

Zooming in to a section, I can see that the return path is very jerky with what seems like many points added all over the place roughly along my path: Zoom in to a problem area

And zooming in more:

Zooming in more

Any idea what causes this to happen and how I can fix/prevent it in the future?

As a side note, what I usually do is export the gps coords from MyTracks to csv, where I draw them using google maps in some javascript I wrote. The above pictures are from that result. Trying to view the path in MyTracks itself usually results i the app freezing, then displaying a blank map or just force closing,

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    The point outside Africa is most likely Lat/Long 0,0. Your results are indicating a poor read, without the ability to fill in the query from a local Wifi either. The system filled in the query with the default value 0,0. In the case where the GPS is just a little off, it probably was able to find a Wifi hotspot to substitute for an approximation for the GPS. For the ones of greater difference, that Wifi is farther away, with a local node calling its "home" hotspot for coordinates. – wbogacz May 9 '15 at 11:57
  • Yes, you are right that 0,0 is the point near Africa (was somewhat amusing when I learned that by looking it up). There are a few 0,0 values in the data as well as values very close to it (like 0.0001), but for most of the hike, there shouldn't be any wifi for me to connect to -it's all forest with maybe one or two other hikers that pass by, nor did I see any houses/buildings. I should have added that during a hike, I turn off the wifi to save power and I don't have data enabled. – mitim May 10 '15 at 1:18

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