def write_waypoint(self, latitude=None, longitude=None, description=None):
        """
        Adds a waypoint to the current task declaration. The first and the
        last waypoint added will be treated as takeoff and landing location,
        respectively.

        ::

            writer.write_waypoint(
                latitude=(51 + 7.345 / 60.),
                longitude=(6 + 24.765 / 60.),
                text='Meiersberg',
            )
            # -> $PFLAC,S,ADDWP,5107345N,00624765E,Meiersberg

        If no ``latitude`` or ``longitude`` is passed, the fields will be
        filled with zeros (i.e. unknown coordinates). This however should only
        be used for takeoff  and landing points.

        :param latitude: latitude of the point (between -90 and 90 degrees)
        :param longitude: longitude of the point (between -180 and 180 degrees)
        :param description: arbitrary text description of waypoint
        """

        if not description:
            description = ''

        latitude = self.format_latitude(latitude)
        longitude = self.format_longitude(longitude)

        self.write_config(
            'ADDWP', '%s,%s,%s' % (latitude, longitude, description[0:50])
        )
Adds a waypoint to the current task declaration. The first and the
        last waypoint added will be treated as takeoff and landing location,
        respectively.

        ::

            writer.write_waypoint(
                latitude=(51 + 7.345 / 60.),
                longitude=(6 + 24.765 / 60.),
                text='Meiersberg',
            )
            # -> $PFLAC,S,ADDWP,5107345N,00624765E,Meiersberg

        If no ``latitude`` or ``longitude`` is passed, the fields will be
        filled with zeros (i.e. unknown coordinates). This however should only
        be used for takeoff  and landing points.

        :param latitude: latitude of the point (between -90 and 90 degrees)
        :param longitude: longitude of the point (between -180 and 180 degrees)
        :param description: arbitrary text description of waypoint