def to_lon format, dp
      return lon if !format
      GeoUnits::Converter.to_lon lon, format, dp
    end
def to_lon format, dp
      return lon if !format
      GeoUnits::Converter.to_lon lon, format, dp
    end
Returns the longitude of this point; signed numeric degrees if no format, otherwise format & dp
 as per Geo.toLon()

 @param   [String} [format]: Return value as 'd', 'dm', 'dms'
 @param   [Number} [dp=0|2|4]: No of decimal places to display
 @return [Number|String} Numeric degrees if no format specified, otherwise deg/min/sec

 @requires Geo