[GRASS-dev] how to add metadata in a raster file?

Hamish hamish_nospam at yahoo.com
Wed Nov 8 22:51:54 EST 2006

Yann Chemin wrote:
> while modifying a Landsat7 import module to read data from the .met
> (metadata) file,
> i wondered how i could store some of this useful information as
> appendix to the raster layer created.
> What is the way to do that in C?

yes, but it is a quite limitted. (40 lines x 80 columns for comments section)

from the command line you can use "r.support title=" to set a title,
and "r.support comment=" to add a comment. This is viewable with r.info.

In C it is done with the History struct, see lib/gis/history.c

see any number of raster modules that output a map, e.g. r.in.xyz:

  /* close raster file & write history */

  G_short_history(outmap, "raster", &history); /* init hist structure */
  G_command_history(&history); /* wrote command line to comments */
  strncpy(history.datsrc_1, infile, RECORD_LEN); /* fill in data source line */
  history.datsrc_1[RECORD_LEN-1] = '\0'; /* strncpy() doesn't null terminate if maxfill */
  G_write_history(outmap, &history); /* write hist structure to disk */

you need to do this *after* you've already closed the map, and then pass
the hist fns the string containing the map name.


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