grass-dev@grass.itc.it wrote: > I have a set of vectory > polygons (call it "polygons_select") and one larger > vector polygon which almost overlaps the previous ones > (call it "eco_clipped_central_appalachian"). Now, I would > like to cut A by B, so I obviously do a v.overlay with > "and". Or as it looks in reality: " v.overlay > ainput=polygons_select atype=area alayer=1 > binput=eco_clipped_central_appalachian btype=area > blayer=1 output=polygons_current operator=and > olayer=1,0,0 --overwrite " Now the resulting > "polygons_current" is missing some polygons, which should > obviously NOT be missing! See attached screenshots: - > polygons_select.jpg is where I start - > polygons_select_WITH_eco_clipped_central_appalachian.jpg > shows the second polygon (in transparent yellow) which I > would like to overlay with the first ones. - > polygons_current.jpg shows with the red arrow, where one > polygon is missing.
I've done some testing. I suspect the origin of the issue might be a bug/feature in v.overlay that prevents it from working reliably in lat/long locations. Please anybody verify. Details follow. I can reproduce the problem reported by Andras [1] with his data [2], which are a lat/long location. Namely, the output of: $ v.overlay ainput=polygons_select atype=area binput=eco_clipped_central_appalachian btype=area output=polygons_current operator=and on my machine is a vector that has the same missing polygon as on Andras' screendump [3]. Fiddling around I reprojected Andras' data into a metric projection (the spearfish60 location), and the v.overlay command as above worked perfect then. Not only the polygon missing on [3] was there, but also the artifact described by Andras in his another report [4] were not present. In this case, can anybody tell if v.overlay is not supposed to be used in lat/lon locations, or is it a bug that can be fixed? Maciek [1]http://wald.intevation.org/tracker/index.php?func=detail&aid=452&group_id=21&atid=204 [2]http://wald.intevation.org/tracker/download.php/21/204/452/227/Testdata_location.tar.bz2 [3]http://wald.intevation.org/tracker/download.php/21/204/452/221/polygons_current.jpg [4]http://wald.intevation.org/tracker/index.php?func=detail&aid=384&group_id=21&atid=204 _______________________________________________ grass-dev mailing list grass-dev@grass.itc.it http://grass.itc.it/mailman/listinfo/grass-dev
