The old style native grid file format that was common in earlier version of GMT is still
supported, although the use of netCDF files is strongly recommended.
The file starts with a header of 892 bytes containing a number of attributes defining the content.
The grdedit utility program will allow you to edit parts of
the header of an existing grid file. The attributes listed in Table B.2
are contained within the header record in the order given (except the -array which
is not part of the header structure, but makes up the rest of the file). As this header
was designed long before 64-bit architectures became available, the jump from
the first three integers to the subsequent doubles in the structure does not occur on a
16-byte alignment. While GMT handles the reading of these structures correctly, enterprising
programmers must take care to read this header correctly (see our code for details).
|