Hi, Have you tried the "Zonal Statistics plugin"?
After enabling this plugin, you can find it in the raster menu - or maybe it is already there by default. It calculates count, sum, min, max, mean at the intersection of a polygon layer (e.g. your polygon layer with building footprints) and a given raster layer (your grid based terrain model). I think it does what you want. Hope this helps, Andreas On 2016-03-10 17:37, Richard McDonnell wrote: > Claus, > It may not be exactly what you want, but one suggestion would be to derive > the centroids from the building polygons (making sure there within the > polygon) and then use the point sampling tool to pull the elevations from > your DSM. of course that will not guarantee that you get the max height > If you can, it may be best to go back to the DSM source, the raw data used to > derive the DSM. If it is, for instance a point cloud dataset, like that from > Lidar, you could select all points within your polygons, then extract only > the points at the apex (first returns), just a thought. > Regards, > > Richard > > On 10/03/2016 11:52, Claus Backalarz wrote: > >> Hi, we are novices in the QIS-world so bear with misunderstandings and >> misconceptions. >> >> We have a raster layer with surface heights called DSM_611_86. Originally it >> is was a plain text file with a header describing number of rows and >> columns, geographically lower left corner etc. Data was the surface heights >> in 6250 rows and 6250 columns. The file was imported without problems with >> "Add raster layer" in QGIS. It is beautiful showed in QGIS2.14 Essen on >> Windows 7. So far no problem. >> >> But we want with (a lot) of polygons representing buildings to select all >> surface heights inside this polygons. The selected heights should afterward >> be saved as a reduced raster layer or, even better, as a shape file of >> points with an attribute for the heights. In other words as a layer of >> points with one and only one attribute, the surface height. >> >> We have tried the plug-in "Point Sampling Tools" and some other hints from >> QGIS home pages, but I seems that select and save heights in the described >> way is "out of scope". >> >> Do anybody have a useful way out of this problem ? >> >> Best regards >> >> Claus B >> >> The information transmitted is intended only for the person or entity to >> which it is addressed and may contain confidential and/or privileged >> material. Any review, retransmission, dissemination or other use of, or >> taking of any action in reliance upon, this information by persons or >> entities other than the intended recipient is prohibited. If you received >> this in error, please contact the sender and delete the material from any >> computer. >> >> _______________________________________________ >> Qgis-user mailing list >> Qgis-user@lists.osgeo.org >> List info: http://lists.osgeo.org/mailman/listinfo/qgis-user >> Unsubscribe: http://lists.osgeo.org/mailman/listinfo/qgis-user > > -- > RICHARD MCDONNELL > GIS SPECIALIST PGD GIS ASSOCSCSI > OPW FRM DATA MANAGEMENT > 52 STEPHENS GREEN, DUBLIN 2. > TEL: 01 6476543 > OPW - Ag féachaint don am atá le teacht - Ag caomhnú ón am atá thart > OPW - Looking to the future - Caring for the past > [1] > Email Disclaimer: http://www.opw.ie/en/disclaimer/ > _______________________________________________ > Qgis-user mailing list > Qgis-user@lists.osgeo.org > List info: http://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: http://lists.osgeo.org/mailman/listinfo/qgis-user Links: ------ [1] http://www.opw.ie/
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