# Cost Surface No sense Results. GRASS

I have some doubts with the generation of a cost surface with r.walk of GRASS. 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:

• 0-10=1;

• 11-maxValue=100

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 :

``````M=1.5W+2.0(W+L)(L/W)^2+N(W+L)(1.5V^2+0.35V*abs(G+10))
``````

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

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?