def mavlink_packet(self, msg):
        '''handle an incoming mavlink packet'''
        type = msg.get_type()
        master = self.master
        # add some status fields
        if type == 'TERRAIN_REQUEST':
            self.current_request = msg
            self.sent_mask = 0
            self.requests_received += 1
        elif type == 'TERRAIN_REPORT':
            if (msg.lat == self.check_lat and
                msg.lon == self.check_lon and
                (self.check_lat != 0 or self.check_lon != 0)):
                print(msg)
                self.check_lat = 0
                self.check_lon = 0
handle an incoming mavlink packet