Hello, following up on a bug report, I added a couple lines to the shaded relief plugin which replaces a nodata value with the mean elevation of the DEM if it is tagged valid. I uploaded the updated plugin as version 2.3 to the plugin repository. Please give it a try. The way to use it is to define a no data value in the transparency tab. There are no UI changes in the plugin. For most of my test cases there was no difference between shaded relief with and without nodata values. This is because typically the slopes around the nodata values are steep (even with the mean elev. in place), and aspect based shading is used which does not depend much on slope. In order to see a difference one has to increase clip values to 89 and 90, so only diffuse reflection is used. In cases where the nodata value is some extreme number replacing the extreme numbers with reasonable ones makes numpy - used for all computations - happier.
It might be possible to put a NULL value in the cells of the shaded relief where the DEM has a NULL value, masking the shaded relief. Would that be desirable ? The main problem there is that the shaded relief is 8bit, so one would have to give up a number. And I am not sure if the geotiff driver supports NULL. On the other hand, it should be possible to transfer nodata cells from one raster to another with other available tools. Is that the case, perhaps with the raster calculator ? For proper nodata support numpy would need to support NULL values in the gradient calculation which is not the case yet but apparently will be in their next release (2.0.0). Andreas _______________________________________________ Qgis-developer mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-developer
