Le mercredi 27 janvier 2016 11:55:01, Ari Jolma a écrit : > Folks, > > I'd like to try to implement the XYZM support since I have some free time. > > Before making a RFC, there are some thoughts/questions/ideas: > > * I made a fork for this work at https://github.com/ajolma/GDAL-XYZM so > I can more easily use travis. > > * I think this is mainly changes in the geometry API and generic methods. > > Are there other drivers than shape, which are affected?
On top of my head: PostGIS, FileGDB, OpenFileGDB, GeoPackage, Spatialite. Probably other RDMBs too (Oracle, MSSQL, ... ?) > Currently shape > driver creates XYZ data from XYM data, that would change, which may > break some code. The way the shape driver currently exposes XYM as XYZ is a hack. I'm not sure many people rely on that, and I think it would be OK to change the behaviour with a cleaner approach. > > * Currently XYM or XYZM data seems to be accepted (by WKT and WKB > importers for example) but not stored in generic objects. Right, M components are skipped/ignored > > * The closeness of XYZ and XYM might need some thought: Yes, the concept of coordinate dimension is ambiguous for 3. getGeometryType() would be needed to know the real interpretation. > For example C++ API for making a adding a XYZ and XYM point to a curve > would be the same. > Currently the method calls Make3D() if the curve is > 2D, which is not ok for XYM data. Indeed, we should likely keep some auto-promotion rules for XY->XYZ but perhaps not for XYM/XYZM. > > Tickets related to this are > > https://trac.osgeo.org/gdal/ticket/6063 > https://trac.osgeo.org/gdal/ticket/6331 > > Are there other things I should know? GEOS methods ignore M AFAIR. Other thought: XYM/XYZM support will have some (unavoidable) compatibility impact on C API users as they will potentially receive new geometry types. > > The target would be 2.1 I guess. > > Ari > > _______________________________________________ > gdal-dev mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/gdal-dev -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
