Andrea Aime wrote: >> We have: >> >> CRS.getHorizontalCRS(3d); >> >> which tries to extract the horizontal part - this is not necessarly >> the 2 first dimensions, it could be anywhere in a n-D CRS. It should >> work for every kind of vertical height except ellipsoidal... In other >> words it will work for many EPSG code but not 4327. >> >> Conceptually we should make it work for 3D ellipsoids as well - I >> just didn't had the time to extend this method to this case yet. > Let me elaborate. Jody tried to make GeoServer generate 3D GML when > data stored in a postgis database had 3 dimensions. > > Doing that is not as easy as it seems, it requires the adaptation > of a lots of code. One element is CRS handling, we have lots of > places where 3d data is reprojected, either to 4326 (think computing > the lat/lon bbox for ogc services) or another srs (think wms or wfs > reprojection). > > If the data is in a 3D crs all of those will fail miserabily, meaning > that it's not even possible to setup a 3d feature type in GeoServer > (the lat/lon bbox computation will fail). I do find it surprising that the these transformations are failing; I thought that was the point of having a real CRS around; allowing users to set up a transformation to fit their assumptions (rather than simply hacking of axis by hand). > But that's not all, even when the new FORCE_2D hint is applied, to > allow flattened data to be reprojected we need to associate the > data to a 2D srs (hence my question). Andrea perhaps we are working too hard here? The GML code is very specific about its treatment of coordinates; it really is just taking the first two ordinates right now (and is not consulting the CRS at all). If I match its assumptions we can just make a new CRS by hacking off the last axis (ie the one matching Coordinate.z).
Gak...perhaps we should look at CoordinateWriter a bit more. > Martin, how hard would it be to make that method work with > ellipsoidal height? Does it require true inspiration > (aka, your knowledge) or is that just mere transpiration (i.e., lots > of work?)? A fair question. Jody ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Geotools-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/geotools-devel
