Iván Sánchez Ortega <ivan <at> sanchezortega.es> writes: > > El Miércoles, 9 de octubre de 2013 07:33:43 Federico Jurio escribió: > > Dear all, I am using WGS84 (4326) and would like to buffer based on meters > > and not degrees. [...] > > Can someone please point me in the right direction? > > If you have a working PostGIS instance, you can get your geometries as PostGIS > geographies, then run st_buffer on them. PostGIS will take care of the dirty > work of finding a more-or-less appropiate projection for buffering the > geography. > > > [buffering in degrees] is the easy way and i'm sure that the accuracy isn't > > the best. > > [reprojecting] probably doesn't have the best performance. > > This begs the question: What do you want to achieve? Accuracy, or performance? > > Personally, if PostGIS geographies aren't available, I'd rather reproject > whole geometries into WGS84 UTM (EPSG:326xx) depending on the centroid's > longitude, then buffer, then project back into WGS84 lat-lon (EPSG:4326). > > Best,
Hi, How about using all that on-the-fly with the amazing OGR Spatialite dialect? ogrinfo -dialect sqlite -sql "select transform(buffer(transform(geometry,26915),10000),4326) as geometry2 from states limit 4" states.shp So, transform 4 features from the Geoserver demo shapefile "states.shp" from EPSG:4326 into 26915, create 10000 metre buffer while in 26915 and transform the buffered features back to EPSG:4326. Try it, it's fast. If you think that there are too many vertices in the result, add "SimplifyPreserveTopology" into SQL. Buffer can sometimes make self-intersections into the resulting polygon but that's no problem either because you can correct them in-th-fly by adding "MakeValid" into SQL. The hardest part is to keep trac of all the paranthesis :))))) -Jukka Rahkonen- -Jukka Rahkonen- _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
