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<span lang="EN-US">Claus,</span><br>
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<br>
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. <br>
Regards,<br>
<br>
Richard<br>
<br>
<div class="moz-cite-prefix">On 10/03/2016 11:52, Claus Backalarz
wrote:<br>
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<blockquote cite="mid:61hgje01adg9m368@seg1.opw.ie" type="cite">
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<p class="MsoNormal"><span lang="EN-US">Hi, we are novices in
the QIS-world so bear with misunderstandings and
</span><span class="hps"><span lang="EN">misconceptions.</span></span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US">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.</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US">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.</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US">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”.</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US">Do anybody have a useful
way out of this problem ?</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US">Best regards</span></p>
<p class="MsoNormal"><span lang="EN-US">Claus B</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
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<div class="moz-signature">-- <br>
<b><u>Richard McDonnell</u></b><br>
<b><small><small><small>GIS Specialist PgD GIS AssocSCSI</small></small></small></b><br>
<b><small>OPW FRM Data Management</small></b><br>
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