Hello all. In the last days I've been working on a script trying to implement the COLTOP method of Jaboyedoff et al., 2009
pdf here: http://www.igc.usp.br/pessoais/guano/temp/Jaboyedoff_etal_2009_Geomorph_Turtle_mountain_DEM.pdf Basically it takes the aspect and slope, calculates the position of this 'vector' in a stereonet (equal-angle projection, same used in structural geology) and assign a color to the coordinates from a HSV color space. This is then used to make a color-shaded DEM, where in theory all possible orientations of lineaments would be visible, overcoming the limitations of common shaded relief maps. So I made a python script (also attached, needs to run on GRASS 7) to calculate compass-oriented aspect values and the radius of a "pole to line" on a stereonet. (Jaboyedoff uses "poles to planes", but I think that using the vector defined by aspect/slope as lineations is easier to interpret). Then I use these values to calculate the RBG values from the HSV colorspace (H=aspect_compass, S=slope_radius, V=fixed value, like 0.7). After that, I multiply the results (which are given in the 0-1 interval) by 255 and write them back to GRASS, where I use r.composite to create the final image. The thing is, the results I get, although you can see the method works, are far from being as nice as the example presented in Jaboyedoff's paper. It seems he did more than just calculate the HSV-to-RBG. Also, it doesn't matter the value of V I use, the r.composite output is always the same. The V value should give me brigther or darker maps. There is some stuff in the script that won't make to the final cut, they are there just to check if the maps were created correctly etc. Also there are some stuff that could be done with r.mapcalc, but i decided to do all in python just to practice. I'd like to get some feedback from you guys on this. best Carlos -- Prof. Carlos Henrique Grohmann - Geologist D.Sc. Institute of Geosciences - Univ. of São Paulo, Brazil http://www.igc.usp.br/pessoais/guano http://lattes.cnpq.br/5846052449613692 Linux User #89721 ________________ Can’t stop the signal.
r.coltop
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