Device.OpenUri(new Uri( geo:Lat,Long)) wrong behaviour

Hi, I'm using this command:

Device.OpenUri(new Uri("geo:"+_branch.Latitude+","+_branch.Longitude));

And it gives different result in both iOS and Android.
In iOS it opens Google Earth and place me in random position, meanwhile in Android it opens google maps and nothing else happen.
Both this behaviour tested in real device. I'd like that when i'll tap a button that call this operation, it will opens iOSMap(on iOS) or GoogleMaps(on Android) and as destionation the coordinate that i setted... Which should be the best way to obtain this? I'm mainly focusing on iOS.