Re: [GRASS-user] r.stream.extract Syntax Problem
[Answering to your latest post in a new thread, but I prefer to keep it all in one thread.] On Tue, Apr 10, 2012 at 1:54 AM, Rich Shepard rshep...@appl-ecosys.com wrote: On Mon, 9 Apr 2012, Markus Metz wrote: The computational region should be aligned to the DEM in order to get accurate results. Aligning to the resolution of the DEM is not enough, i.e. you should use g.region align=DEM instead of g.region res=XXX -a. r.stream.extract should work if only a subregion is to be analysed by setting the computational region accordingly and/or creating a MASK e.g. for a specific basin. Markus, madi, et al.: The region does need to be set with a mask (in my case, and based on the v.to.rast output of the individual subbasins). v.to.rast? Basins as created by r.watershed, r.stream.basins and r.water.outlet are already raster maps. The last advice in the example on the manual page is to compare the weighted and unweighted extracted stream maps and see which looks better. As a newcomer to this module I have no experience on what better looks like. Attached are two .pdf files. One shows the weighted output streams, the other the unweighted output streams. Both have the vector streams overlaid on them. The weighted output has a solid yellow background and I don't know what that represents. In this case there is indeed no answer to what looks better because both look terrible, to be honest. Something terrible must have happened to the DEM, or there are indeed completely flat areas in the west. If the aim is to extract streams that resemble the digitized vector lines, the DEM you used seems to be not suitable. You could try to run r.stream.extract with the DEM as the only input and a larger threshold. The region should be aligned to the DEM first with g.region -p align=dem. If that produces reasonable results, you can try to fine-tune by adjusting the threshold and supplying a (weighed) accumulation map as additional input. Markus M PS: Please do not change the thread all the time. With regard to this subject, you have started now the 7th or so thread, I lost count, impossible for anyone to follow. ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.stream.extract Syntax Problem
On Sat, 7 Apr 2012, Margherita Di Leo wrote: Do you produce any null cells when you weight the flow acc? I'm not sure but I guess this could also be a problem (?) madi, I don't know. How do I determine if null cells are produced (look at r.null.fill output, perhaps)? Rich ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.stream.extract Syntax Problem
Rich, On Mon, Apr 9, 2012 at 10:07 PM, Rich Shepard rshep...@appl-ecosys.comwrote: On Sat, 7 Apr 2012, Margherita Di Leo wrote: Do you produce any null cells when you weight the flow acc? I'm not sure but I guess this could also be a problem (?) madi, I don't know. How do I determine if null cells are produced (look at r.null.fill output, perhaps)? You said you produce the accumulation map by: r.mapcalc elevation.10m.acc.weighed = elevation.10m.acc * weight The map namely weight shouldn't have null values (use r.null to set null values to zero). Best, madi -- Ing. Margherita Di Leo, Ph.D. ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.stream.extract Syntax Problem
On Sat, 7 Apr 2012, Micha Silver wrote: Maybe the MASK is somehow interfereing ?? Micha, This is apparently not the issue. I followed Helmut's suggestion and set the proessing region using the vector boundary of one subbasin. Still the same error: accumulation map does not match elevation map. What would be very helpful in fixing this mis-match is understanding in what way the accumulation map does not match the elevation map. Is it the region (set to the elevation map) or some other parameter? Rich ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.stream.extract Syntax Problem
On Sat, 7 Apr 2012, Micha Silver wrote: Maybe the MASK is somehow interfereing ?? Micha, I wondered about this. The unweighted accumulation map does not generate the error, yet the same mask is applied. But, this may be why the weighted accumulation map does not throw an error if the entire elevation map is the analytical unit. Each of my two current projects requiring spatial analyses involve multiple 12-digit HUC basins (sub-watersheds). I need to separately analyze each sub-watershed to determine differences. I can clip vector maps by interescting the lines and the sub-watershed boundaries. But, my understanding is that raster maps cannot be subdivided in the same way so we need to generate masks for the areas to be included in each analysis. That is, r.* modules are applied to only those portions of the overall DEM map within the mask. If there is a module, or process (perhaps applying r.mapcalc for the map algebra), that will allow me to create separate DEMs for each sub-watershed (or other analytical unit) I would prefer to work with each of those rather than need to run r.mask for each different basin. I'd like to learn how to sub-set raster DEMs so each basin is a separate map rather than a masked portion. Thanks, Rich ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.stream.extract Syntax Problem
On Sat, 7 Apr 2012, Margherita Di Leo wrote: That's what I thought. Or else a g.region problem?? madi, In this case r.stream.extract would through an error for the unweighted accumulation map, too. Unless weighing each cell in the accumulation map changes the region in a way that's not obviously visible? Rich ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.stream.extract Syntax Problem
Rich, On Sat, Apr 7, 2012 at 3:39 PM, Rich Shepard rshep...@appl-ecosys.comwrote: On Sat, 7 Apr 2012, Margherita Di Leo wrote: That's what I thought. Or else a g.region problem?? madi, In this case r.stream.extract would through an error for the unweighted accumulation map, too. Unless weighing each cell in the accumulation map changes the region in a way that's not obviously visible? Do you produce any null cells when you weight the flow acc? I'm not sure but I guess this could also be a problem (?) madi Rich __**_ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/**mailman/listinfo/grass-userhttp://lists.osgeo.org/mailman/listinfo/grass-user -- Ing. Margherita Di Leo, Ph.D. ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.stream.extract Syntax Problem
Hi Rich, AFAIK (but surely Markus Metz will give an insight) r.stream.extract must run with flow accumulation produced by r.watershed. In order to use a weighted flow accumulation, I would produce it using the r.watershed command with the option flow, instead of mapcalc. HTH madi On Thu, Apr 5, 2012 at 11:29 PM, Rich Shepard rshep...@appl-ecosys.comwrote: I'm learning to use r.stream.extract by following the detailed example on the manual page. The last two steps are to extract steam maps using both weighted and unweighted accumulation maps. The example syntax is: # extract streams r.stream.extract elevation=elevation.10m@**PERMANENT \ accumulation=elevation.10m.**acc.weighed \ threshold=1000 \ stream_rast=elevation.10m.**streams And the example syntax to create the weighted flow accumulation map is: # weigh accumulation map r.mapcalc elevation.10m.acc.weighed = elevation.10m.acc * weight For one of my sub-watersheds I ran the following: r.mapcalc dem10m.acc.weighted = dem10m.acc * weight (all on one line but it may wrap to two lines when you view it). I check that this worked properly by displaying demm10m.avg on d.mon x0, then displaying dem10m.acc.weighted on the same monitor. The two maps are congruent. So, when I run r.stream.extract I get an error that the accumulation map does not match the elevation map from which r.mapcalc created it: r.stream.extract elevation=dem10m.avg accumulation=dem10m.acc.**weighted threshold=1000 stream_rast=dem10m.streams (NOTE: again, all on one line, but may display on two lines.) Load input maps and get start points... ERROR: Accumulation map does not match elevation map! There is no error with the unweighted accumulation map (dem10m.acc). I'm not seeing why this error is generated, and need to understand why so I can model a dozen or so small basins. TIA, Rich __**_ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/**mailman/listinfo/grass-userhttp://lists.osgeo.org/mailman/listinfo/grass-user -- Ing. Margherita Di Leo, Ph.D. ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.stream.extract Syntax Problem
On Fri, 6 Apr 2012, Margherita Di Leo wrote: AFAIK (but surely Markus Metz will give an insight) r.stream.extract must run with flow accumulation produced by r.watershed. In order to use a weighted flow accumulation, I would produce it using the r.watershed command with the option flow, instead of mapcalc. madi, As I wrote, I've been following the example on the manual page, so # calculate flow accumulation r.watershed ele=elevation.10m@PERMANENT acc=elevation.10m.acc -f I've run r.watershed elev=dem10m.avg accum=dem10m.acc -f Rich ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.stream.extract Syntax Problem
Rich, On Fri, Apr 6, 2012 at 5:41 PM, Rich Shepard rshep...@appl-ecosys.comwrote: On Fri, 6 Apr 2012, Margherita Di Leo wrote: AFAIK (but surely Markus Metz will give an insight) r.stream.extract must run with flow accumulation produced by r.watershed. In order to use a weighted flow accumulation, I would produce it using the r.watershed command with the option flow, instead of mapcalc. madi, As I wrote, I've been following the example on the manual page, so # calculate flow accumulation r.watershed ele=elevation.10m@PERMANENT acc=elevation.10m.acc -f I've run r.watershed elev=dem10m.avg accum=dem10m.acc -f I meant something like: r.watershed ele=elevation.10m@PERMANENT acc=elevation.10m.weight_acc flow=weight -f Rich __**_ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/**mailman/listinfo/grass-userhttp://lists.osgeo.org/mailman/listinfo/grass-user -- Ing. Margherita Di Leo, Ph.D. ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.stream.extract Syntax Problem
-- Micha Silver 052-366-5918 -Original message- From: Rich Shepard rshep...@appl-ecosys.com To: grass-us...@lists.osgeo.org Sent: Fri, 06 Apr 2012, 20:16:48 GMT+02:00 Subject: Re: [GRASS-user] r.stream.extract Syntax Problem On Fri, 6 Apr 2012, Margherita Di Leo wrote: I meant something like: r.watershed ele=elevation.10m@PERMANENT acc=elevation.10m.weight_acc flow=weight -f followed by: GRASS 6.5.svn :~/grassdata r.stream.extract elev=dem10m.avg accum=dem10m.acc.weighted thresh=1000 stream_rast=dem10m.lm.streams Load input maps and get start points... ERROR: Accumulation map does not match elevation map! [Raster MASK present] Maybe the MASK is somehow interfereing ?? Still the same error generated. I'm quite puzzled ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
