[GRASS-user] RE: r.terraflow on massive DEM

[Thayer Young]

With regards to the size of DEM, if you can get the command to run it may take several days to finish, this is more than twice the size of the Washington State DEM that took the authors 33 hours in 2003 (Arge, Chase, Halpin, Toma, Urban, Vitter, Wickremesinghe  Efficient Flow Computation on Massive Grid Terrain Datasets Geoinformatica Volume 7 Issue 4, December 2003 Pages 283 - 313 ).  My mid-2014 computer runs at about twice the speed quoted in the paper.
Did you r.recode it to make it smaller?  In flat areas you need the data contained after the decimal point to allow the flow a chance to make it down hill, otherwise you can get streams going no where near where they do in real life.  I have never tried running r.terraflow on an integer raster, I know that it works on decimal rasters.

-Thayer

 
   
Date: Mon, 12 Jan 2015 09:59:40 -0200
From: Daniel Victoria <daniel.victoria at gmail.com>
To: grass <grass-user at lists.osgeo.org>
Subject: [GRASS-user] r.terraflow on massive DEM
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    <CA+irsJjf7xhWgU968D+4+xc2YGJ=_n4xJtP0_WeU1ZpoRTt9ng at mail.gmail.com>
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Hi list,

I'm trying to run r.terraflow on a very large DEM but I wander if it's
__too large__.

The region dimensions are:
ncol=141114
nrow=140487
Data type = CELL

The map is actually a reclass map of a raster that I imported using
r.external.

When I run r.terraflow I get:

r.terraflow elevation=srtm_brasil at PERMANENT filled=srtm_fill
direction=flowdir swatershed=sink accumulation=flowacc tci=srtm_tci
directory=E:\terraflow_temp

WARNING: raster srtm_brasil is of type CELL_TYPE --you should use
r.terraflow.short
ERROR: [nrows=140487, ncols=141114] dimension_type overflow -- change
dimension_type and recompile
(Mon Jan 12 09:57:18 2015) Command finished (0
sec)

However, I don't have an r.terraflow.short command
I'm running Grass 7.0.0beta4 from OsGeo4W

Cheers
Daniel
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