[GRASSLIST:3920] Re: worldwide SRTM data now available

[Hamish]

An update on the ETOPO2 data, it is actually elevations for both
above and below sea level at 2' (3.7-km-sq) horizontal resolution.


Download: (111mb)
http://www.ngdc.noaa.gov/mgg/global/relief/ETOPO2/


Load into a Lat/Lon location with this command:

r.in.bin -s input=ETOPO2.dos.bin output=etopo2 \
  title="worldwide 2' topography (3.7km-sq)" \
  bytes=2 rows=5400 cols=10800 n=90N s=90S e=180E w=180W


Recolor with this command (GRASS 5.3.0+):

r.colors etopo2 rul=terrain

(I edited the color map in the $MAPSET/colr/ directory to make the
oceanic fade to black happen at 10000m depth, not 500m depth)


Resulting snapshot is attached.


To make it look good in NVIZ, I had to scale it with:
r.mapcalc "etopo2_scaled=etopo2/(60*1852.0)"

This makes the XYZ into degrees*deg*deg instead of deg*deg*meters;
then you need to redo the colors.

Perhaps a better solution in NVIZ is called for when dealing with
lat/lon projections? Assume meters? see shade.clr.sh fix for this.



Great stuff.

I think this would make a nice GRASSNews newsletter sidebar article, but
I can't find much time right now. I'll try and put something together
over the next day or two, but maybe not.



Hamish
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