[GRASS-user] r.viewshed add-on is taking too long

[Chaulio Ferreira]

Hello everyone,

I've been trying to compute some viewsheds using the r.viewshed module (available in http://grass.osgeo.org/wiki/GRASS_AddOns), but it's taking to long to finish. 

I ran this module on a 5000x5000 (95mb) raster grid and it took 3min 17sec to finish. I have seen some articles where it's said that this module is capable of computing raster grids bigger than this one in 18 seconds. I also tested it on a bigger raster grid (33000x33000, 4.05gb), and it took almost 3 days to finish!

So, I was wondering if I've been doing something wrong, because the execution times seem to be much bigger than the expected.

I'm using an Intel Core 2 duo 2.93GHz, with 4GB RAM and Ubuntu 10.04 32bits. My GRASS version is GRASS 6.4.3svn. The command line I used was:

r.viewshed -b --overwrite input=r9_5000 at PERMANENT output=vs_r9_5k coordinate=2500,2500 obs_elev=50 tgt_elev=50 memory=2000

I used coordinate=2500,2500 because the terrain bounds are X:0~5000 and Y:0~5000 and I wanted the observer to be sited at the center of it. I had tried to import this same raster grid (using r.in.bin) with smaller bounds (X:0~50 and Y:0~50) and to run r.viewshed with coordinate=25,25, but I received the following assertion error:

Determine visibility...
r.viewshed: statusstructure.cpp:73: float get_vertical_angle(Viewpoint, StatusNode, surface_type, int): Assertion `fabs(sn.dist2vp) > 0.001' failed.
Aborted


Does anyone use this Add-on and has some running times to show me and compare with mine? Or does someone knows if I am doing something wrong?

Thanks,

Chaulio Ferreira
 		 	   		  
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