Hei Helumt, In that case I would probably try r.param.scale in order to identify flat areas at maybe different scale levels.
V-valleys have a higher variation in aspect at the bottom (sides are almost facing each other and nearly "meet" at the lowest point in a V-valley). While sides are more or less steep. So slope and aspect at a coarser level (also available through r.param.scale) could help to distinguish V- and U-valleys. Depending on scale U-Valleys have a TPI of ~0 at the bottom and ~0 at the middle of the sides (equaly much terrain above and below a focal cell in the given neighborhood). Some background material on TPI can be found here: http://www.jennessent.com/arcview/tpi.htm Jenness used ArcView. Yet TPI is a simple combination of r.neighbors and a mapcalc. Good luck with your modelling. Cheers, Stefan -----Original Message----- From: grass-user-boun...@lists.osgeo.org [mailto:grass-user-boun...@lists.osgeo.org] On Behalf Of Helmut Kudrnovsky Sent: 1. april 2014 10:33 To: grass-user@lists.osgeo.org Subject: Re: [GRASS-user] calculation valley floor width in GRASS or some index indicating valley floor width? Hi Stefan, thanks your response. >If you think of valleys in a hydrological perspective I would have a >look at r.stream. modules for having a kind of threshold above streams (in m), and then use r.grow.distance for an inverted valley representation. >If you think of valleys in a geomorphometric context things might be a >bit more complex (esp. for U-valleys, compared to V-valleys). it's maybe a mixing of both... ;-) given is a habitat typical for gravel beds/braided river in mountain regions. it seems the probability of the occurrence of the needed habitat structure is greater in wider valleys floors than in narrow valley floors, and greater in U-valleys than in V-valleys. the idea is to get some measure/index to handle this probability ... ----- best regards Helmut -- View this message in context: http://osgeo-org.1560.x6.nabble.com/calculation-valley-floor-width-in-GRASS-or-some-index-indicating-valley-floor-width-tp5132402p5132410.html Sent from the Grass - Users mailing list archive at Nabble.com. _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
