set gcs location

def cmd_antenna(self, args):
        '''set gcs location'''
        if len(args) != 2:
            if self.gcs_location is None:
                print("GCS location not set")
            else:
                print("GCS location %s" % str(self.gcs_location))
            return
        self.gcs_location = (float(args[0]), float(args[1]))