Moritz, Thanks heaps for the script. It's really is useful and will facilitate the adoption of i.segment. It certainly would be a nice addition to the wiki page.
Unfortunately I can't comment too much on this, as my object-based classification projects are on hold, but I'll try to give that a shot sometime soon. It could also be interesting to try non-supervised approach using i.segment to limit the "salt and pepper" noise affecting such classifications. Cheers, Pierre 2013/10/31 Moritz Lennert <mlenn...@club.worldonline.be>: > Hello, > > Based on the great work on i.segment by Eric and MarkusM, I've been trying > to put up a complete workflow allowing object-based image classification in > GRASS. Conclusion: it is possible with currently available tools, even > though some components would be nice to have in addition. Attached you can > find a simple shell script which shows all the steps I went through. I > commented it extensively, so it hopefully is easy to understand. > > Some remarks: > > - This only works in GRASS 7. > > - It uses the v.class.mlpy addon module for classification, so that needs to > be installed. Kudos to Vaclav for that module ! It currently only uses the > DLDA classifier. The mlpy library offers many more, and I think it should be > quite easy to add them. Obviously, one could also simply export the > attribute table of the segments and of the training areas to csv files and > use R to do the classification. > > - At the top of the script are a series of parameters that have to be > defined before being able to use the script as such (but the script is more > meant as a proof-of-concept than as a real script) > > - Many other variables could be calculated for the segments: other texture > variables (possibly variables by segment, not as average of pixel-based > variables, cf [1]), other shape variables (cf the new work of MarkusM on > center lines and skeletons of polygons in v.voronoi), band indices, etc. It > would be interesting to hear what most people find useful. > > - I do the step of digitizing training areas in the wxGUI digitizer using > the attribute editing tool and filling in the 'class' attribute for those > polygons I find representative. As already mentioned in previous discussions > [2], I do think that it would be nice if we could have an attribute editing > form that is independent of the vector digitizer. > > More generally, it would be great to get feedback from interested people on > this approach to object-based image classification to see what we can do to > make it better. > > > Moritz > > [1] https://trac.osgeo.org/grass/ticket/2111 > [2] http://lists.osgeo.org/pipermail/grass-dev/2013-February/062148.html > > _______________________________________________ > grass-dev mailing list > grass-dev@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/grass-dev -- Scientist Landcare Research, New Zealand _______________________________________________ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev