Use either the left or right model.
The model on the left, the PanTo often glitches when making frequent, fast calls to poll the LocationChanged event but usually does work. 
The rightmost model using CenterFromString always works. 
Be aware, the gps does not read immediately, it may take 30 to 60 seconds to achieve a satellite fix,
therefore I recommend this construction that will not trigger until the device achieves it's first satellite fix (when the latitude and longitude are no longer 0, the default value prior to a satellite fix).
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