Hi Moritz, I'm not sure what you mean by 'Maris' first part of the solution'. I saw only one part to Maris's suggestion (refining the region's resolution) because I said in my initial mail that I had set extents of the region to the contours_20m vector layer. Initially I did have a resolution of 20m and got an empty raster layer as a result.
I share Micha's confusion about this. Although it doesn't make much sense to have a 20m cell size (my bad) I would have thought that v.to.rast would still have given me an output. Regards Hanlie 2011/5/3, Moritz Lennert <[email protected]>: > On 03/05/11 15:47, Micha Silver wrote: >> On 05/03/2011 04:34 PM, Moritz Lennert wrote: >> >>> On 03/05/11 10:20, Micha Silver wrote: >>>> On 05/03/2011 09:11 AM, Hanlie Pretorius wrote: >>>> >>>>> Hi Maris, >>>>> >>>>> Thanks, your suggestion worked. With the region's resolution set to >>>>> 5m, I got some output. >>>>> >>>> >>>> Hi Maris: >>>> Sorry for butting in on this, but I don't understand why the region >>>> resolution should make any difference to v.to.rast?? >>>> Would you mind to explain? >>> >>> From the v.to.rast manual: >>> >>> "v.to.rast will only affect data in areas lying inside the boundaries >>> of the current geographic region. Before running v.to.rast, the user >>> should therefore ensure that the current geographic region is >>> correctly set and that the region resolution is at the desired level." >>> >> >> >> Thanks, Moritz >> What I'm trying to understand is the question about resolution. Would >> you expect, as >> Hanlie indicted, to get *no output* in the raster because of too course >> resolution? >> He claims that at 20m x 20m v.to.rast of a line feature created all NULL >> cells, but at 5m x 5m the lines did appear in the raster. >> ?? > > Hanlie didn't tell us whether he applied Maris' first part of the > solution as well (but I guess he did): > > g.region vect=contours_20m > > I agree with you that resolution does not make the difference. However, > I guess that Maris meant that having a 20m resolution seems too coarse > for 20m contour lines, but even that is not clear as all depends on the > topography of the region in question. If you have 100m altitude change > for 50m horizontal change, then 20m is a bad choice of resolution, but > if you have 100m altitude change for 1km horizontal change, it should be > more than enough. > > So, in conclusion, the region's resolution setting can make a huge > difference in v.to.rast, but in this particular case does not explain > why there was no output. This is certainly linked to the region's extension. > > Moritz > > _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
