Margherita, now I got your point...I had a very similar problem a short time ago, but finally I was able to solve it. If your are interested in, take a look to the following notes - I know, a bit complicated but it works
- set your desired path as a mask for limiting following calculations using r.mask - r.describe -dr <your_dem> to fetch min and max of elevation along your path (use tool awk or any other string processing function like split() in Python) - r.to.vect to convert the mask into a vector line, and then v.to.db -p <your_vector_path> option=length column=s to print out the path length (therefor, parse the string again to fetch the column that contains the length) - now you can calculate the slope based on altitude difference and distance... Perhaps it is adaptable to yours... Christian. From: Margherita Di Leo Sent: Wednesday, June 02, 2010 6:50 PM To: Christian Schwartze Cc: grass-user@lists.osgeo.org Subject: Re: [GRASS-user] get coords from a raster Christian, thank you for answering. My problem is that I don't want to use the slope map to get slope, bu i want to calculate it as the ratio between the difference of the elevation and the distance between two given points (pixels). To do that, I need to get the coordinates of the points as a input file for r.profile. Margherita 2010/6/2 Christian Schwartze <christian.schwar...@uni-jena.de> Why are you not using r.statistics, since it takes one base map (your path as a raster) and another map containing data you want to analyze (your slope). With the "average" option/method you will get the desired result, if I understand you correctly... Christian. From: Margherita Di Leo Sent: Wednesday, June 02, 2010 6:17 PM To: grass-user@lists.osgeo.org Subject: [GRASS-user] get coords from a raster Hi List, I'm trying to make a script to calculate the slope along a path. I want to calculate the slope as the average of cell per cell slope. For my purpose I found r.profile to produce the input file for my script, but I have to give it the coordinates of the points. As I have a raster and not a vector, I was wondering if is there a non interactive way like a d.where or something like that, that i can use for my purpose. I mean, i have a raster in which there is the path i'm interested in, and the other cells are null. Thank you in advance Margherita ------------------------------------------------------------------------------ _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
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