Hi Patrick- > I'm trying to find documentation on the internal structure of the gempak > data files. Is this documented and if so where can I find it? There is some documention in the GEMPAK distribution in the gempak/txt/gemlib directory. In particular, dmlib.txt explains the basic DM (Data Management) structure. The other files explain specific implementations for grids (gdlib.txt), surface (sflib.txt) and sounding (snlib.txt). It also helps to look through the source code for the dm library to look at how the different sections are structured. Don Murray Ticket Details =================== Ticket ID: EOL-525821 Department: Support GEMPAK Priority: Normal Status: Open