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I was wondering how Google Maps on my Android phone can locate me with a good accuracy when my GPS is disabled.

At first I though it was with the cell tower but I'm not sure it can achieve this precision and it is way better when the wireless is enabled.

  1. If Wifi is ON and GPS is ON = Perfect location
  2. If Wifi is ON GPS OFF = Still Perfect location
  3. If Wifi is OFF and GPS is ON = location is not presisce.

Tested this with 5 -6 Phones

Any Idea why ?

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3  
Um... isn't '2' the same as '1'. You may want to correct your typo? –  MappaGnosis Apr 16 '12 at 18:39
    
How 'accurate' are you talking about, and how are you measuring it? Is (1) giving you the same numbers every time when you return to a specific location? Or are you reading an estimated position error somehow? –  Simbamangu Apr 17 '12 at 8:15
    
SylvesterSneekl = I corrected the point 1 and 2. @Simbamangu - I am zooming the map to the maximum. and that i can see a hugh the differene in the location approx 30 -50 meter –  Adi Mathur Apr 17 '12 at 8:54

1 Answer 1

From your comment, it sounds like you are seeing a different position on your map when you use wireless networks (cell / wifi) or GPS.

Firstly, wireless networks can give very accurate positions depending on how much georeferencing data was available for your area – within 2-3 metres, which is as good as most GPS fixes.

That said, there are a few things that come to mind:

  1. The GPS is having difficulty getting a good position due to poor sky view, and/or interference from buildings or other sources (some recent discussion of this on GIS.se if you search). If the GPS fix is poor, then the application may just ignore it and use the wireless fix only.
  2. The GPS might be right, and both the map you're seeing and the wireless fix wrong!

If you're in a city in Europe or North America, then (1) seems likely - interference from buildings, yet lots of wifi/cell towers to give you a good wireless fix. Otherwise I might suspect (2) – I know that Google Maps is off by 20-150m for most of the city where I live in East Africa, and there is not enough cell tower or wifi georeference data for our area to give good fixes.

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@Adi Mathur - would be very interested to hear if you find out if any of these ideas were actually the problem! –  Simbamangu Apr 19 '12 at 15:38

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