Please keep the thread on the list. Yes I think it's inappropriate to split a watershed into 2 parts if you want to model the whole thing as one. You are likely going to do better finding a single projection that covers your entire area of interest.
-Alex On 03/16/2016 10:20 AM, Mourad Boutouchent wrote: > IS it wrog if I split up my DEM in two parts, the 1st one in the UTM21N and > the rest in the UTM22N then I can run Grass hydrological moudles (r.watershed > and r.water.outlet among other) on each DEM and finally merge them in GRASS > or QGIS. Think you this is an appropriate way to do it? > > ------------------------------------------------------------------------------------ > Mourad Boutouhent > Laboratoire de Mathématiques Informatique et Applications > Université de Guyane > Tél : 06 63 81 50 29 > > -------------------------------------------- > En date de : Mer 16.3.16, Alex Mandel <[email protected]> a écrit : > > Objet: Re: [GRASS-user] define a region by 2 epsg > À: "Mourad Boutouchent" <[email protected]>, > [email protected] > Date: Mercredi 16 mars 2016, 16h50 > > How far into the second > UTM Zone does your region go? If not far and the > distortion is acceptable you can reproject 1 > into the other. > > Otherwise > you need to find or create a Projection that does a better > job > of covering your region. A UTM > projection is unlikely to be a good > candidate in this case. Do you care more about > preserving Area or > Distance measures (that > will help you pick an appropriate projection). > > So, no, you can not use 2 EPSG > codes at the same time, you have to > convert > the data into a common projection. > > Thanks, > Alex > > On 03/16/2016 08:10 AM, Mourad Boutouchent > wrote: > > I'm working on watershed > hydrology, then I went to obtain drainage direction, > accumulation zones, streams system and elementary watersheds > of a study area. However I work on an area which belong to 2 > EPSG (EPSG 3313 and EPSG 2972). > > > > I download all the SRTM tiles of the study > area and have filled the voids. I merged these tiles and > projected the result in the EPSG 2972 (initially WGS84). Of > course, a part of the DTM has negative EAST coordinates > which cause errors when assinging region and running > r.watershed and r.water.outlet. > > I tryed > to work in WGS84 but still r.water.outlet does not work. > > > > Is it possible to > define a region with two EPSG? How achieve r.water.outlet > with success > > I'm quite locked...Any > help ? > > > > > > ------------------------------------------------------------------------------------ > > B.Mourad > > > Laboratoire de Mathématiques Informatique et > Applications > > Université de Guyane > > Tél : 06 63 81 50 29 > > > _______________________________________________ > > grass-user mailing list > > [email protected] > > http://lists.osgeo.org/mailman/listinfo/grass-user > > > > _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
