[GRASS-user] r.watershed / r.terraflow - huge area (amazon)

[Carlos Grohmann]

Hello all

I'm working on deriving a nice drainage network for the Amazon basin. The
problem is that the area is too large.

The region settings are these:
projection: 3 (Latitude-Longitude)
zone:       0
datum:      wgs84
ellipsoid:  wgs84
north:      6:17N
south:      21:30S
west:       80:37W
east:       44:50W
nsres:      0:00:03
ewres:      0:00:03
rows:       33340
cols:       42940
cells:      1431619600

With 14.3 billion cels, r.watershed would need about 450 GiB of disk space
running in seg mode, is that correct? (from the manual, 31 MB for 1 million
cells).

I do have that disk space available, but it's in a secondary drive. If I
set TMPDIR to that drive, will r/watershed use it? I ask because the
documentation (https://grass.osgeo.org/grass72/manuals/variables.html) only
says that this environmental variable is used by "[Various GRASS GIS
commands and wxGUI]".

On a side note, r.terraflow should be an alternative for such a large
dataset, but from the manual:
"r.terraflow has a limit on the number of rows and columns (max 32,767
each)".
That's the size of a positive short integer. Is this limit still needed?


thanks

Carlos




-- 
Prof. Carlos Henrique Grohmann
Institute of Energy and Environment - Univ. of São Paulo, Brazil
- Digital Terrain Analysis | GIS | Remote Sensing -

http://carlosgrohmann.com
http://orcid.org/0000-0001-5073-5572
________________
Can’t stop the signal.
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