Amagine wrote: > Thanks Martin, I'll have a look at terrain analysis in grass. See > what I can come up with. > >>> I would like to be able to regulate the following parameters: >>> >>> Minimum height of peak >> >> A topographic "peak" will have an elevation, not a range of >> elevations. So I'm not sure what you mean. > > I should have elaborated further. > > Minimum height of peak, meaning do not classify any peaks below a > set minimum threshold : 1000 m for instance.
You can use r.mapcalc for that, after r.param.scale, like: r.mapcalc 'peaks_1km=if(dem>=1000,peaks,null())' >>> Minimum drop of surrounding peaks >> >> Not sure what you mean here too. > > Meaning a peak is not extracted if there are surrounding elevations > within a minimum drop amount eg. 50m or 100m (depending on accuracy > of DEM file and refinement desired of distinct peaks) Maybe you could use slope, calculated from dem, to filter these out with r.mapcalc? >>> summit points optional hierarchy... >>> >> >> I guess these are technical mountaineering terms? So again I'm not >> sure what data you are hoping to extract. > > Summit points.... The highest point on a peak. pseudo-pseudo code: r.cluster: create a raster map where each peak has a unique value r.info -r: find out the number of peaks for each summit do : r.mask: set a mask to match one of the peak spots created by r.cluster r.mapcalc: extract the peak falling into this spot r.info -r: find out it's max value r.mapcalc: extract the reported max (summit) into another raster done r.patch: patch all summits, if needed > So a peak encompasses all vertical surface areas within the "Summit" > point based on the above two categories. > > I suppose I define a peak as a categorical area, and a summit as a > point. Perhaps there are better definitions. > > Hierarchy in my mind would be to classify peaks within peaks. Based > on the initial two parameters (Minimum height of peak, minimum drop > of surrounding peaks) > > I suppose I should draw a picture :) probably make more sense. I hope I got you right. Best Maciek _______________________________________________ grassuser mailing list [email protected] http://grass.itc.it/mailman/listinfo/grassuser
