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I have a major problem that I hope someone can help with. On my Google Maps feature under my Location History it shows a location that I was never at at any point, but when my wife happened to see that location she doesn't believe me that the GPS could be wrong and pinpoint that location if I was never there.

I was first wondering myself how could that could be possible if I was never there or my phone was never at that location that was 35 miles away from me and second is there any way I could prove the GPS being wrong? Can I contact Google Maps and can they give an official printout of that certain day and every location I was? I really need to prove my honesty to her and hope there is a way.

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4 Answers 4

From Google's Location Source and Accuracy page:

Data sources

The following location data sources may be used to derive location:

  • GPS: GPS accuracy can be up to several meters depending on your GPS signal and connection. Your phone must support GPS, have it enabled, and allow Google Maps access to it.

  • WiFi: WiFi (wireless network) accuracy should be similar to the access range of a typical WiFi router, or about 200m or better. Your phone must support WiFi and have it enabled.

  • Cell ID: Cell ID (cell tower) accuracy depends on cell tower density and available data in Google's cell ID (cell tower) location database. Accuracy may be approximated at distances up to several thousand meters. Note: Some devices do not support cell ID location.

...

Note: When Latitude is running in the background, it will default to cell ID (cell tower) location on most phones to preserve your battery life.

So if you didn't have Google Maps open for any reason at the time of the erroneous location, it will have defaulted to it's least accurate location finding service, that depending on the density of cell towers in that area (generally more dense in urban areas, less dense out in the countryside) could be out by several kilometers.

If you visit the Location History page in your Google account on a PC, at https://maps.google.com/locationhistory/b/0 then it should show a similar map and listing of places as you see on your phone, but you can also click each recorded location to see how (in)accurate it was. When you click the blue dot for a location, Google draws a blue circle around it that shows approximately the (in)accuracy of that location fix.

Location History accuracy circle

The picture above shows an inaccurate fix that covers 3 villages, and a number of roads (I was actually on a train at the far southern edge of that blue circle).

As long the problem location fix has a large blue circle around it, and you can account for being somewhere in that blue circle then you should be ok.

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At first, I couldn't see any blue dot areas. Then I realized that I had to zoom in to see anything (because I had GPS on and thus had a very accurate reading for each location). Thanks for pointing out this feature! –  Stephen Schrauger Apr 29 '13 at 15:56
    
@Jason, I found some points of mine that had great accuraccy, but I know are also incorrect. But they are within a quarter mile or less from where I actually was, and I imagine GPS was off and it used WIFI (and as I work at a campus, the wifi is the same SSID everywhere). So even if the blue dot doesn't cover where you actually were, it should cover an area close to where you actually were. The accuracy is an estimate, after all. –  Stephen Schrauger Apr 29 '13 at 16:04

That's most likely not a GPS position, but rather a WiFi hotspot. Google's location service makes use of different identifiers:

  • GPS
  • WiFi hotspots
  • Cell towers

While GPS should be quite accurate (bad conditions might give lower accuracy, but usually shouldn't place you too far off), and cell towers usually are not moving -- WiFi hotspots may exactly do that. I will give you an example situation to understand:

Say, Google's "StreetView cars" passed my house/flat in NYC 2 years ago, while my homy WiFi hotspot was turned on. So they recorded my hotspot's SSID, and connected it with the current GPS location. 6 month later, someone passing by my NYC home with "network location" turned on, gets a fine (and relatively accurate) position from that: location service asked Google's database about my hotspot's SSID, and got the coordinates back.

Fine, so far -- but a year ago I decided to move to San Diego. I completed that 6 month ago, and set up my WiFi hotspot again. Now you pass by my house, your device detects my SSID, asks Google for that hotspot's location... and suddenly you are in NYC, as Google did not update its database yet!

That's how it mostly happens -- and that's how I traveled hundreds of miles in a few seconds a couple of times (my ears still ringing from that acceleration, as I also traveled back a few seconds later)...

To prove you're unlikely having been there, check your other stored locations and check their timestamps. Try to find some with a timestamp close to the wrong location. Once it turned out you must have traveled light-speed to make those data becoming true, the error should become obvious.

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I have that problem too on my daily commute I suddenly get "relocated" to the next village while walking to the train station. I wonder thoug how I can fix that. Can I report this to google? –  Marcel Feb 3 at 12:10
1  
Not that I know. I wonder why we are forced to share our data with Google (when using network location). The "official reason" was exactly that. But they do not seem to care... –  Izzy Feb 3 at 12:56

If you click on the dots, you will get the time it recorded you there. If it is 35 miles away, and it is within minutes of the previous location, then it would be impossible for you to be there in less than 1/2 hour. I also agree with the others about the Wi-Fi. I was traveling in Michigan this week, and there is one point in Las Vegas that shows up just 10 minutes after the previous position in Michigan. Someone's internet connection was being sent out to the network from Vegas.

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replace the wife. it seems that she trusts unreliable technology more than you :-)

GPS uses best estimate statistical methods to guess at the location, and sometimes the calculation goes wild due rounding errors, lousy code in the GPS chip, etc. etc.

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The problem is not GPS, which is really very accurate, albeit not always available. The problem is that the "location" calculation, in order to save battery, uses data from a number of sources far less accurate than GPS. –  Ben Voigt Oct 21 '13 at 17:48

protected by Community Dec 1 '13 at 18:58

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