visad/src/main/java/ucar/nc2/iosp/gempak/GempakSoundingIOSP.java
@Override
  public boolean isValidFile(RandomAccessFile raf) throws IOException {
    if (!super.isValidFile(raf)) {
      return false;
    }
    // TODO:  handle other types of surface files
    return gemreader.getFileSubType().equals(GempakSoundingFileReader.MERGED) ||
            gemreader.getFileSubType().equals(GempakSoundingFileReader.UNMERGED);
  }
@Override
  public boolean isValidFile(RandomAccessFile raf) throws IOException {
    if (!super.isValidFile(raf)) {
      return false;
    }
    // TODO:  handle other types of surface files
    return gemreader.getFileSubType().equals(GempakSoundingFileReader.MERGED) ||
            gemreader.getFileSubType().equals(GempakSoundingFileReader.UNMERGED);
  }
Is this a valid file?

@param raf RandomAccessFile to check
@return true if a valid Gempak grid file
@throws IOException problem reading file