Farrukh Najmi wrote: > Dear colleagues, > > Looking at geotools GML code its not clear to me how it uses the srid > and userData fields of the com.vividsolutions.jts.geom.Geometry class. > Which GML code did are you looking at specifically? - SAX parser? I think it sets the srsName to the userData object - DOM parser? - XDO parser? - XSD-XML parser?
In general I don't know what these parsers do for a JTS Geometry object; because the CRS information is stored at the Feature level in GeoTools right now (there is no set convention for how to handle JTS Geometry srid name and userData object; because that convention would be for a specific application.) > What are these fields set to when a JTS Geometry is stored after being > mapped from a GML geomtery? > GML Geometry comes back as a JTS Geometry with the correct coordinates > What are these fields set to when a JTS Geometry is read back before being > converted to a GML Geometry? > > Specifically: > > Does the persistent JTS Geomtery object's always have srid defined? > no it does not. > Is there a userObject always specified to stored the srsName? > no it does not. > Does the srid and srsName refer to the CRS used by GML representation? > The GML specification only talks about srsName; we have chosen to convert this information into a CoordinateReferenceSystem and hold it as part of the FeatureType information. > Why do we need need to store both srid and srsName? > We don't need to store either. > Thanks for any guidance. > I am sorry this is such a muddle for your; JTS Geometry is defined by the Simple Feature for SQL specification and does not really line up with GML in any way (literally they are a different model at a very technical level; JTS has LineStrings, GML has Curves made up of LineStrings). We are faking this mapping for you because JTS is available now and works - some information (like GML srsName) is lost along the way. Now if you would like the srsName to be saved as the userData object by each and every parser; that may be a good idea - and we can take it up with the developers list. 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-gt2-users mailing list Geotools-gt2-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/geotools-gt2-users
