30ASDEMDCW data with grass

Bill Brown brown at gis.uiuc.edu
Tue Oct 17 11:33:30 EDT 1995


Yes, I have used this data for Haiti and Europe.  

1. uncompress the .bil file into your cell directory

2. create an ascii header file for it (or run r.support & edit header)
   Here's my header for eur_30_dem1:
	proj:       3
	zone:       0
	north:      85N
	south:      35N
	east:       22:30E
	west:       25W
	cols:       5700
	rows:       6000
	e-w resol:  0:00:30
	n-s resol:  0:00:30
	format:     1
	compressed: 0

3. next I ran r.mapcalc to get real negative numbers instead of unsigned
   r.mapcalc eur_30_dem1a="if(eur_30_dem1>32768,eur_30_dem1-65536,eur_30_dem1)"

   (This creates a smaller file due to automatic compression.)

4. Then run r.support to create a color file.  You will probably have to
   edit the color file because they use the value -9999 for no data so
   you may want to assign a specific color to that, then use the remaining
   range for a color ramp.  For Haiti, I just made all -9999 data zero since
   there was no "real" zero data.  r.stats can help you find the real 
   Here's my colr file for eur_30_dem1a:
	% -9999 4536
	-30:150:230:150 0:10:230:10
	0:10:230:10 492:10:160:10
	492:10:160:10 962:50:130:10
	962:50:130:10 1514:120:100:30
	1514:120:100:30 2067:120:130:40
	2067:120:130:40 2481:170:160:50
	2481:170:160:50 2757:235:235:100
	2757:235:235:100 4536:255:255:200

5. Now you can get rid of the file eur_30_dem1:
   g.remove eur_30_dem1
   g.rename eur_30_dem1a,eur_30_dem1

- Bill

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