[GRASS-dev] Re: [GRASS GIS] #1577: r.stream.extract/r.stream.order - "calculated" mainchannel vs. "real" mainchannel
what does it means? Any reference? Main channel established in real network or algorithms of modeling main channel? the mentionned "real" mainchannel is the part of real Austrian river network (i.e. listed in the annual Austrian hydrographical handbook as the river 'Isel') >>an example screenshot of river basin in the eastern part of the alps is attached >where it is? it's in the ticket, see http://trac.osgeo.org/grass/attachment/ticket/1577/mainchannel4.gif Helmut - best regards Helmut -- View this message in context: http://osgeo-org.1560.n6.nabble.com/GRASS-GIS-1577-r-stream-extract-r-stream-order-calculated-mainchannel-vs-real-mainchannel-tp4473866p4474065.html Sent from the Grass - Dev mailing list archive at Nabble.com. ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
[GRASS-dev] Re: [GRASS GIS] #1577: r.stream.extract/r.stream.order - "calculated" mainchannel vs. "real" mainchannel
>> the mentionned "real" mainchannel is the part of real Austrian river network (i.e. listed in the annual Austrian hydrographical handbook as the river 'Isel') or may have also a look in the pdf mentioned in http://wisa.lebensministerium.at/article/archive/29373 Helmut - best regards Helmut -- View this message in context: http://osgeo-org.1560.n6.nabble.com/GRASS-GIS-1577-r-stream-extract-r-stream-order-calculated-mainchannel-vs-real-mainchannel-tp4473866p4474112.html Sent from the Grass - Dev mailing list archive at Nabble.com. ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
[GRASS-dev] Re: [GRASS GIS] #1577: r.stream.extract/r.stream.order - "calculated" mainchannel vs. "real" mainchannel
Hi, Jarek: >> the mentionned "real" mainchannel is the part of real Austrian river >> network >> (i.e. listed in the annual Austrian hydrographical handbook as the river >> 'Isel') >It is popular argument against algorithmic approach. Usually computer >algorithms cannot reproduce arbitrary human decisions :-( Markus M: >As Jarek said, there is nothing like the one and only "real" >mainchannel because there a different definitions on how to determine >the main channel. You would need to get the definition of "real >mainchannel" out of the Austrian hydrographical handbook, in this example it's based on hydrographical characteristics: - the "real" mainchannel (river Isel) has an (nival)/gacial runoff regime - the calculated mainchannel (river Schwarzach) has an nival runoff regime, and flows into the river Isel Jarek, Markus M, thanks a lot for the insight! best regards Helmut - best regards Helmut -- View this message in context: http://osgeo-org.1560.n6.nabble.com/GRASS-GIS-1577-r-stream-extract-r-stream-order-calculated-mainchannel-vs-real-mainchannel-tp4473866p4475056.html Sent from the Grass - Dev mailing list archive at Nabble.com. ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
Re: [GRASS-dev] Re: [GRASS GIS] #1577: r.stream.extract/r.stream.order - "calculated" mainchannel vs. "real" mainchannel
On 02/15/2012 04:46 PM, Helmut Kudrnovsky wrote: what does it means? Any reference? Main channel established in real network or algorithms of modeling main channel? the mentionned "real" mainchannel is the part of real Austrian river network (i.e. listed in the annual Austrian hydrographical handbook as the river 'Isel') It is popular argument against algorithmic approach. Usually computer algorithms cannot reproduce arbitrary human decisions :-( an example screenshot of river basin in the eastern part of the alps is attached where it is? it's in the ticket, see http://trac.osgeo.org/grass/attachment/ticket/1577/mainchannel4.gif Helmut Ok, this is not software issue. In attached example calculated main channel is evidently longer than real main channel so software cannot calculate it different. On my first look there are two possibilities: - first: main channel is established according to basin area. If so try to model stream network using SFD and next Gravelius hierarchy using accumulation map as an option. Result should be correct. This is impossible using MFD approach - second: main channel is arbitrary chosen as "central channel". No idea how to reproduce it without complex analysis of basin shape and network topology. J. - best regards Helmut -- View this message in context: http://osgeo-org.1560.n6.nabble.com/GRASS-GIS-1577-r-stream-extract-r-stream-order-calculated-mainchannel-vs-real-mainchannel-tp4473866p4474065.html Sent from the Grass - Dev mailing list archive at Nabble.com. ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
Re: [GRASS-dev] Re: [GRASS GIS] #1577: r.stream.extract/r.stream.order - "calculated" mainchannel vs. "real" mainchannel
On Wed, Feb 15, 2012 at 10:46 PM, Helmut Kudrnovsky wrote: > what does it means? Any reference? Main channel established in real network > or algorithms of modeling main channel? > > the mentionned "real" mainchannel is the part of real Austrian river network > (i.e. listed in the annual Austrian hydrographical handbook as the river > 'Isel') As Jarek said, there is nothing like the one and only "real" mainchannel because there a different definitions on how to determine the main channel. You would need to get the definition of "real mainchannel" out of the Austrian hydrographical handbook, maybe modify input accumulation for r.stream extract and then use the best matching method in r.stream.order. Markus M ___ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
