Geolocator and accuracy in Windows Phone 8 - windows-phone-7

Question

I have a few questions about Geolocator and property DesiredAccuracy.
I have the method GetMyPosition:
public async Task<Geoposition> GetMyPosition()
{
Geoposition myGeoposition = null;
Geolocator myGeolocator = new Geolocator();
myGeolocator.DesiredAccuracy = PositionAccuracy.High;
try
{
myGeoposition = await myGeolocator.GetGeopositionAsync();
return myGeoposition;
}
catch (Exception ex)
{
Deployment.Current.Dispatcher.BeginInvoke(() =>
{
MessageBox.Show("Can't get the position");
});
return null;
}
}
1) Why
Geolocator.DesiredAccuracy = PositionAccuracy.High;
Geolocator.GetGeopositionAsync();
always return Geoposition.Coordinate.PositionSource = Cellular with accuracy 400 - 1600 m (on device Nokia Lumia 520)?
2) Under what settings I can get a high accuracy (50 - 100 m) and PositionSource = Satellite?
3) If I have the loaded maps on my device and I activated the airplane mode on the device, then code
Geolocator myGeolocator = new Geolocator();
myGeolocator.DesiredAccuracy = PositionAccuracy.High;
try
{
myGeoposition = await myGeolocator.GetGeopositionAsync();
return myGeoposition;
}
will work? Without a celluar, only a satellite?
4) How strong is the precision of coordinates depends on the device?
Thanks in advance!

Answer 1

Taken from MSDN
Although the Location Service uses multiple sources of location information, and any of the sources may not be available at any given time (for example, no GPS satellites or cell phone towers may be accessible), the native code layer handles the work of evaluating the available data and choosing the best set of sources. All your application needs to do is to choose between high accuracy or the default, power-optimized setting. You can set this value when you initialize the main Location Service class, GeoCoordinateWatcher.
C#
GeoCoordinateWatcher watcher = new GeoCoordinateWatcher(GeoPositionAccuracy.Default);
So it seems like you can't control which source is used but rather the available source will be used based on the specified position accuracy on GeoCoordinateWatcher. Try initializing a GeoCoordinateWatcher with high accuracy and see what happens
var geoWatcher = new GeoCoordinateWatcher(GeoPositionAccuracy.High);

Answer 2

You can use
Geolocator myGeolocator = new Geolocator();
myGeolocator.DesiredAccuracyInMeters = 20;
...
to explicitly state how accurate you want the location to be which would allow the device to manage its power a little better but whether you get close to that accuracy with your result depends on the quality of the location the device can get. If you're inside a building for example you're not going to get something that accurate without connecting to WIFI