GRASS 4.2.1 (V.18, V.19, ...) and GRASS 5 offer two ways to import data from the GTOPO30 worldwide elevation datacase (and GLCC maps / GLCC info).
1. So, get the data for your region.
2. Look at the .GIF file, if you like.
3. Check the .PRJ file for the projection. We need this info for creating the GRASS location later.
4. Find out the boundaries for your area (East and North positive):
Latitude (row) Longitude (col) Elevation Tile Minimum Maximum Minimum Maximum Minimum Maximum Mean Std.Dev. ------- ---------------- ---------------- -------------------------------- W180N90 40 90 -180 -140 1 6098 448 482 W140N90 40 90 -140 -100 1 4635 730 596 W100N90 40 90 -100 -60 1 2416 333 280 W060N90 40 90 -60 -20 1 3940 1624 933 W020N90 40 90 -20 20 -30 4536 399 425 E020N90 40 90 20 60 -137 5483 213 312 E060N90 40 90 60 100 -152 7169 509 698 E100N90 40 90 100 140 1 3877 597 455 E140N90 40 90 140 180 1 4588 414 401 W180N40 -10 40 -180 -140 1 4148 827 862 W140N40 -10 40 -140 -100 -79 4328 1321 744 W100N40 -10 40 -100 -60 1 6710 375 610 W060N40 -10 40 -60 -20 1 2843 212 168 W020N40 -10 40 -20 20 -103 4059 445 298 E020N40 -10 40 20 60 -407 5825 727 561 E060N40 -10 40 60 100 1 8752 1804 1892 E100N40 -10 40 100 140 -40 7213 692 910 E140N40 -10 40 140 180 1 4628 549 715 W180S10 -60 -10 -180 -140 1 2732 188 297 W140S10 -60 -10 -140 -100 1 910 65 124 W100S10 -60 -10 -100 -60 1 6795 1076 1356 W060S10 -60 -10 -60 -20 1 2863 412 292 W020S10 -60 -10 -20 20 1 2590 1085 403 E020S10 -60 -10 20 60 1 3484 893 450 E060S10 -60 -10 60 100 1 2687 246 303 E100S10 -60 -10 100 140 1 1499 313 182 E140S10 -60 -10 140 180 1 3405 282 252 W180S60 -90 -60 -180 -120 1 4009 1616 1043 W120S60 -90 -60 -120 -60 1 4743 1616 774 W060S60 -90 -60 -60 0 1 2916 1866 732 W000S60 -90 -60 0 60 1 3839 2867 689 E060S60 -90 -60 60 120 1 4039 2951 781 E120S60 -90 -60 120 180 1 4363 2450 665 ANTARCPS -90 -60 -180 180 1 4748 2198 1016 (this table was taken from GTOPO30 readme)
5. Start GRASS and create a new location
6. Accept, if valid and specify the ellipsoid ("spheroid" in .PRJ file: wgs84).
7. Accept creating the mapset. Now you have entered GRASS.
8. Proceed with data importing like described below:
------------------------------------------------------------------------- a) use the standard module "r.in.ll" to import in a lat/long region ------------------------------------------------------------------------- Ex: r.in.ll -s input=E020N90.DEM output=gtopo30 bpc=2 corner=sw,40:00:15N,20:00:15E dimension=6000,4800 res=30,30 spheroid=wgs84 ------------------------------------------------------------------------- b) use "r.in.bin", a new module in GRASS 4.2.1/5.0, which is similar to r.in.ascii, to import in any region (here: lat/long). ------------------------------------------------------------------------- Ex: r.in.bin -bs input=E020N90.DEM output=gtopo30 bytes=2 north=90 south=40 east=60 west=20 r=6000 c=4800 (you can add "anull=-9999" if you want sea level to have No data value)9. Look at the data or calculate something...