How are product files compressed?
Product files as a whole are generally not compressed; but individual SDSs within each product file may be compressed, usually by using the hrepack utility. The same routine can be used to unchunk and decompress the SDSs, by choosing the compression method “NONE” and chunking info of “NONE”. If $HDFBIN/hrepack doesn’t exist on your system, go to the HDF Tools website to get a copy. MODAPS uses a lossless compression method (GZIP) for compressing the SDSs. Therefore, compressing an HDF SDS will have no effect on the contents of the SDS as read by HDF library routines. Those routines check whether or not the SDS is compressed, and decompress the data, if necessary, without requiring any special action on the part of the user. A program that reads the SDS, and never checks whether it’s compressed, or tries to write to it, will work the same with compressed data as with uncompressed ones. Reading a compressed SDS is slower than reading an uncompressed SDS, but that effect can be minimized
