code: function(gpsRefPos) {
      if(gpsRefPos === undefined || 
         gpsRefPos.length < 4) {
        this._gpsRefPos = undefined;
      }
      else if(gpsRefPos[0] === 0 && 
              gpsRefPos[1] === 0 && 
              gpsRefPos[2] === 0 && 
              gpsRefPos[3] === 0) {
        this._gpsRefPos = undefined;
      }
      else {
        this._gpsRefPos = gpsRefPos;
      }
      return this.redraw();
    }
docs: Sets the position offset of the silouette to the center of the symbol.
  The array contains the refpoints from ITU R-REC-M.1371-4-201004 page 108
  in sequence A,B,C,D.
  @method setGPSRefPos
  @param gpsRefPos {Array} The GPS offset from center.