Hi all reviving this old thread because I'm interested in using the z-value (elevation) from kml files (type wkbMultiLineString25D) in a qgis plugin.
Are there any plans to introduce z-value (25D) support in 2.0? Experimenting has shown that doing geom.exportToWkt() strips the z-value. How can I currently handle z-values? I understand that I would have to parse the wkb directly, is this possible in python? If so can someone give me some pointers? Other option - external python library like shapely? It seems shapely does support z levels. Or would it be simpler to parse the kml files by hand using an xml parser, as syntax is relatively simple? regards, Etienne On Mon, Dec 5, 2011 at 8:02 AM, Marco Hugentobler < [email protected]> wrote: > > > > > > > > > > > > > Hi Paul > > Unfortunately, the current geometry system does not handle z- and > m-values in a sound way. > Some tools consider z and others don't. M-values are even more difficult > as they cannot be accessed by the QGIS API (z-coordinates can be read by > parsing the binary format of the geometry). > > An overhaul of the geometry system is planned for version 2. > > Regards, > Marco > > On 05.12.2011 10:42, Paul Lens wrote: > > Hi all, > > > > 1. I made a TIN surface, using the interpolation plugin, from a point > > shapefile (with "ALTITUDE" field) and 3D line shapefiles. I lost time > > trying to extract the relevant lines from the line shapefiles without > > loosing the 3D information (Z values of the nodes). > > If I remember well, I first used "Merge Layers" from the mmqgis > > plugin, and it kept the Z information. Than, I used the Intersection > > command in the Vector menu, and the Z information was lost. Finally, > > after manually selecting the relevant lines and using "save as", I got > > the expected 3D line shapefile keeping the Z values. > > Is this loss of Z information a known limitation of the gdal vector > > commands in QGIS (vector menu) and is this limitation affecting all > > these commands? Or did I do something wrong? > > > > 2. In a second step, I wanted to be able to easily see (through > > labeling a Z field) or ask (with the identify command) those Z values > > from the 3D lines, so as to fine tune the interpretation of the > > topography. > > Again the gdal tool (in Vector menu) "Node Extraction" lost all Z > > information. > > Is there a workaround to create a point shapefile with a Z field? Or, > > at least, to keep the Z values in a point shapefile, rasterize it so > > as to be able to visualize the Z value using the "Identify" command > > on the raster? > > > > Thanking all the developers for this wonderful program, > > > > > -- > Dr. Marco Hugentobler > Sourcepole - Linux& Open Source Solutions > Churerstrasse 22, CH-8808 Pfäffikon SZ, > [email protected] http://www.sourcepole.ch > Technical Advisor QGIS Project Steering Committee > > > > _______________________________________________ > Qgis-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-user > >
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