[GRASS-user] r.walk doubt

Luis Miguel Royo Pérez luis.miguel.royo at gmail.com
Fri Sep 5 05:26:30 PDT 2014

Hi everyone,

I have some doubts with the generation of a cost surface with /r.walk/ . 
It's assumed that the resulting layer is measured in seconds, but when I 
try to convert seconds in days march (6h per day), the resulting layer 
has no sense.

This is the workflow I'm following:

*1st.-* I have several vector layers as roads, rivers, bridges, and a 
raster layer of elevation.

*2nd.-* Rasterize the vector layers with a field named "weight" (PESO in 
spanish) where I have weighted this variables according to if they 
facilitate the walking or not. Reclassify is made if it's needed.

*3rd.-* Find Slope (in percent) layer and reclasify as follow:





*4th.-* r.cross with all the rasterized layer. (roads, bridge, river and 
reclassified slope).

*5th.-* I create a new friction layer using this formula proposed by 
Pandolf (1977) with /r.mapcalc/ :


*6th.-* With this layer measured in Watts I use /r.walk/ with default 

*7th.-* Once obtained this layer measured in seconds I try to convert it 
in hours dividing 3600 and then convert these hours in days march 
dividing 6 (6 hours per day).

Well, the results are not what I expected, the max data of this layer is 
about 8.000... No sense, it should be something like 3 or 4 days, maybe.

*/Here are the files 
I'm using to do this workflow./*

I don't know what I'm missing, maybe is the 4th step wrong? Maybe the 5th?

Another point of view would be nice to me. If you need more info, please 
ask for it and I will add to the question.

Thank you very much to everyone.

Thanks a lot!

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