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
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