Re: [GRASS-user] Strahler order starting from vector data?
W dniu 25.01.2011 13:03, Hamish pisze: Hi, I see v.strahler and r.stream.order in addons can assign Strahler Order to a river network, but how to run that if you are starting with an existing vector river network with no raster DEM? Ordering existing river network (without DEM) require topologically correct network I can guarantee that r.stream.order can order a network created by automatic software like r.stream.extract or r.watershed but not about network digitized manually. There are lots of topological and directional checks, but such tool is possible in the feature if really needed could you cross with a matching coastline vector to extract end nodes at the river mouths? With map algebra for example I can cut river network in any place and order it will even a rough DEM like SRTM data be better than nothing in that case? yes, but it not guarantee that river network will be exactly reproduced how good does it have to be? would etopo1 be ok? (1 arc-minute ~ 2 km cells) Depending the resolution end extend you need. also, how to get around attaching lake and swamp areas which split the river vector line in two? This is unresolved problem in a general case of network ordering. In general lake is treated as a flat area where stream pass trough. (see r.watershed of GRASS 7 with beautify flat areas for details). There are some early proposition of Mark from early 80s (I do not remember the title but I can search if you interested) how to treat such structures but there are no common agreement about it. On the other hand lake shall be treated as local depression. This is implemented in r.watershed and r.stream.extract for GRASS7 convert their boundaries to lines and treat it as a braided river? fill them in then r.thin Same as above. No common ordering system for braided rivers. This problem is commonly called in discussion by hydrologists, but as long as there were no uniform ordering system for braided we can do nothing them somehow? otherwise topology would be clean. how about if the river goes into a cave and out somewhere else? Another unresolved problem. r.stream was created for terrestrial areas not karst system. Modeling of karst system require completely different approach need to trace that gap by hand? (may be too big for the sloppy= option) Probably yes Jarek ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] r.neighbors - annulus (torus) neighbor
Hi all! while I need annulus (or torus) neighbor to some of my work I added easily it to neighbors (grass 65 delev) module. Because I do not won't to create a fork of that module I put it on that url: http://www.staff.amu.edu.pl/~jarekj/r.neighbors2.tar.gz Annulus neighbor is a circular neighbor but with exuding nearest neighborhood defined by inner radius. Maybe someones will find this useful. regards Jarek ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] r.param.scale curvatures: are really OK
Hi while I modified r.param.scale for my purposes I noticed that some formulas for curvatures differs from that I know: for example: plan curvature: is (2.0 * (b * d * d + a * e * e - c * d * e) / pow(e * e + d * d, 1.5)); probably shall be: ( (b * d * d + a * e * e - 2.0 *(c * d * e)) / pow(e * e + d * d, 1.5)); profile curvature: is return (-2.0 * (a * d * d + b * e * e + c * e * d) / ((e * e + d * d) * pow(1.0 + d * d + e * e, 1.5))); probably shall be: return (- (a * d * d + b * e * e + 2.0* (c * e * d)) / ((e * e + d * d) * pow(1.0 + d * d + e * e, 1.5))); Of course threre could be reasons why little different formulas are used but I do not see any. This formulas is in grass 6.4, 6.5 and 7.0 and I assume in older version too. regards Jarek ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.stream.basins error
W dniu 12.10.2010 09:49, Francesco Mirabella pisze: Hi, thanks for you message, the modules were compiled from the add-ons about one week ago, I suppose they should be the updated version. What do you mean by "unique streams"? If you mean the number of streams which come out from the operation, these are about 7500. Do you think is the area too large? BTW I was successful with r.watershed on the same dataset but I just wanted to test these new modules Francesco Jarek Jasiewicz wrote: Francesco Mirabella pisze: Hi all, I am trying to generate a basins map from a dem using r.stream.basins I first cut the dem to the area I want to work on than run g.region to set the region to this map. Then I calculated streams and streams flow directions with r.stream.extract. In order to get stream basins I used r.stream.basins: r.stream.basins dir=rivers_flowstream=rivers basins=basins_rivers The output gives an error saying: Reading maps... Calculate basins using streams... Finding nodes... ERROR: Stream and direction maps probably do not match (Mon Oct 11 11:15:28 2010) Comando terminato (0 sec Why do they not match if I derived them with the same command and from the same dem ? Am I doing something wrong ? such errors appears when region dir map and stream map comes from different operations. Try if you are using most actual r.stream.extract and r.stream basins modules. How much unique streams you have created with r.stream.extract? thanks in advance Francesco ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user GRASS 6 or 7? This error appears when the number of possible outlets overcome the allocated memory for given raster. Memory is allocated as a sum of vertical and horizontal resolution times 2. If the number of possible outlets overcomes that values the error is throwing. In most standard network this allocation is enough and is stored as a bug-handler to avoid crashes or infinite loops if user will use maps from different sources. If you have a 7500 streams and you have raster map grater than 2000x2000 cells it should not happen. If not I have a problem. For future use: if you find any problem with continuosly developed software (like these in add-ons) first: - give us more information about version, of your GRASS and add-on - try to reproduce this error on standard GRASS dataset like SPEARFISH or NC if error canot be reproduced: - give us more information of data type you are using: resolution, region etc. ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
