To get the phone's current geo-location, altitude, speed, .. you can use the following:

If location is not available for any reason, then NULL will be returned.

So you should handle that:

if (position == null)
{
     await Alert.Toast("Your location is not available. Please try again later.");
     return;
}
else
{
      // Now you can use the position data
}

Shortcut to the above:

The above scenario is quite common. So instead of writing all of the above code yourself, you can just call the RequestOrGetCurrentPosition() method.

var position = Device.Location.RequestOrGetCurrentPosition();
if (position != null)
{
    // Just use it. All due error messages will have been shown.
}

Using the result

The result is an instance of the following class:

public class GeoPosition
{
     // Always provided:
     public double Latitude;
     public double Longitude;
     public double Accuracy;

     // May or may not be provided.
     public double? Altitude;
     public double? AltitudeAccuracy;
     public double? Speed;
}

As you can see the if you want to use Altitude and Speed properties, your code should handle the scenario of them not being returned.