I'm slowly beginning to find clues for solving my problem of how to grid the scattered 3D data. The Objective Analysis example is one clue but this seems geared toward interpolating scattered data onto a 2D grid. I'm not sure if Ferret will do what I want, so I'm also looking at a package called "Surfer for Windows". Donald R. Newcomb Naval Oceanographic Office, N531 Stennis Space Center, MS