问题
I'm trying out a Windows Phone 7 Maps application which tracks the device. I'm displaying a textblock which updates the current speed using "e.Position.Location.Speed.ToString("0.00")" from the "GeoPositionChangedEventArgs e" argument passed to the PositionChanged event handler of "GeoCoordinateWatcher" object.
While debugging the application in emulator, I used a set of previously recorded push pins and played the emulation. The longitude/lattitude positions change properly but the speed is reflected as NAN.
Why is this happening? How is the speed property calculated?
回答1:
Moving you call to separate thread will fixed the problem...
GeoCoordinateWatcher location not returning speed. NaN instead
来源：https://stackoverflow.com/questions/9258193/geocoordinatewatcher-is-not-getting-geocoordinate-speed-in-emulator