Michal there is not a tool for that, but you can easily create a workflow in SEXTANTE to get the result you need
1) calculate the perimeter of each polygon with the "add geometry columns" algorithm 2) calculate a circularity measure with the field calculator (see here: http://en.wikipedia.org/wiki/Shape_factor_(image_analysis_and_microscopy) ) 3) select based on it. If you want to select a given percentage of the "most-circular" shapes, you can normalize the circularity measure with the field calculator as well, so you can easily select the N most circular ones or the x% of them. Regards 2013/3/26 Michał Bełcik <belcikmic...@gmail.com>: > Hi everyone > > Is there any tool in Sextante to select polygons by their shapes? For > example, I would only like to select those that are more or less circular, > and not thin and extended in length. Is there any way to select them by > their width to length ratio or anything similar? > > All the best > > _______________________________________________ > Qgis-user mailing list > Qgis-user@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/qgis-user > _______________________________________________ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-user
