This field format is used to read 2D or 3D regular grids of arbitrary dimensions in the popular Flexible Image Transport System (FITS) image format. A popular library for reading and writing FITS image in C or FORTRAN is CFITSIO, which must be installed for DisPerSE to be able to use this kind of files.

This file format is also used for storing HEALPIX tesselations of the sphere. DisPerSE will automatically detect if the FITS file contains a HEALPIX tesselation.