code: public void addGGA( GGASentence gga ) {
          try {
              if (gga.isValid()) {
                  gpsFixQuality = gga.getFixQuality();
                  position = gga.getPosition();
                  altitude = gga.getAltitude();
                  if (time == null) {
                      time = gga.getTime();
                  }
              }
          } catch (Exception e) {
              // ignore it, this should be handled in the isValid,
              // if an exception is thrown, we can't deal with it here.
          }
      }
docs: Method to add a new {@link GGASentence}.
  
  @param gaa the sentence to add.