Hi, Le mardi 19 octobre 2010 à 12:02 +0200, Chris Browet a écrit : > > Even for France, it is not so easy as it seems: what they are > able to > get are PDFs from which they extract vector information. This > is then > imported in JOSM with a coordinate transform (they have five > or six > different projections for France). For each town, the result > has to be > "fixed" for hundreds of buildings which have impossible or too > complicated shapes in the cadastre, before they can finally > import it. > The process takes at least half a day of volunteer work for > each town. > > This is the process to get vectorial (actually an SVG) from a PDF > printed from the Cadastre site. > > > The "less hacky" way (and, AFAIK, the way the JOSM plugin work) is to > request WMS images from the site and use it to draw over. > Using the WMS requires and handful of http request before being > useable though... > > > Furthermore, not the complete french cadastre is actually vectorized. > Some places only have scanned images.
As a french contributor (I live between Rijsel and Doornik), I can clarify things. We have two main ways to work with the cadastre. First with JOSM who draws a layer from the cadastre's WMS. You have to draw over. It is still used to get streets and their names. We can also get useful data : churches names, town hall, schools, post office, wayside crosses … To get buildings, the more usefull way is a script who downloads PDF files from the cadastre's website. This pdf contains SVG data, so the script runs pdf2svg. The SVG is turned into a OSM file by a perl script (using GDAL). This file only contains buildings and waterway shapes. Files can be found here : http://osm.cleo-carto.org/cadastre/ Some people are working on a Merkaartor plugin and some improvements of the script. Without waiting the kadaster's release you can already work with the SPOT Image WMS. It doesn't cover Belgium, but the borders with France are. I had a quick look and towns such as Doornik, Kortrijk or Koksijde appear. It's bad resolution pictures (1px for 2.5m), but it's very useful for landuse. It's also very accurate (~70cm) so you can fix GPS-based ways. Big building, such as warehouses, appears clearly. I hope this mail is helpful. Philippe _______________________________________________ Talk-be mailing list Talk-be@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-be
