As of Ferret version 2.30, netCDF is the suggested format for data storage (see the chapter, "Converting to netCDF"). This section describing TMAP information is included only for users who already work with data in TMAP format.
To access TMAP-formatted data sets use
SET DATA_SET TMAP_set1, TMAP_set2, ...
If the directory portion of the filename is omitted the environment variable FER_DESCR will be used to provide a list of directories to search. The order of directories in FER_DESCR determines the order of directory searches. If the extension is omitted a default of ".des" will be assumed (if the filename has more than one period, the extension must be given explicitly).
For every TMAP-formatted data set there is a descriptor file containing summary information about the contents of the data set. This includes variable names, units, grids, and coordinates. When the command SET DATA_SET is given to Ferret pointing to a GT-formatted or TS-formatted data set, it is the name of the descriptor file that must be specified.