Store the location in a process global variable. In the second process you should check whether Location.IsInitialized returns true before you access it.
This solution works only if one assumes that the person does not move. - Or you accept a tolerance of 400m (in this example, radius = 200m).
As long as the person is not moving from the area - LocationChanged is not triggered. (the global variable is not updated)
If I come from 'Task2' (and read the global variable) I always have position the center (start). but the person could (now) also be at position a or positon b.