code: def get_distance_metres(aLocation1, aLocation2):
      
      dlat = aLocation2.lat - aLocation1.lat
      dlong = aLocation2.lon - aLocation1.lon
      return math.sqrt((dlat*dlat) + (dlong*dlong)) * 1.113195e5
docs: Returns the ground distance in metres between two LocationGlobal objects.
  
      This method is an approximation, and will not be accurate over large distances and close to the 
      earth's poles. It comes from the ArduPilot test code: 
      https://github.com/diydrones/ardupilot/blob/master/Tools/autotest/common.py