<html><head></head><body>Thanks Lene. Why not creating a model and adding it to shared repo?<br>
All the best.<br><br><div class="gmail_quote">Il 1 febbraio 2016 09:33:47 CET, Lene Fischer <lfi@ign.ku.dk> ha scritto:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<pre class="k9mail">Hi Again,<br />I have found tree solutions for my problems- Can anyone tell me if they are correct.<br /><br />I clip the DTM with the polygon and the use the SAGA Real surface area. It gives me a new raster where the pixelvalues has changed from Z to a calculated area. Finally I use the Zonal statistic and add the SUM value to the polygon.<br /><br />The second is a Grass function r.surf.area It gives me an area in the log.<br /><br />The functions has a slightly different result, but it´s only 3/1000 :-)<br />----------<br /><br />For calculating the fence I had to be a bit more old school. Distance= SQRT((x2-x1)^2 + (y2-y1)^2 + (z2-z1)^2) I took the polygon and converted it to points with a ordered pointnumber. <br />Used the SAGA function Add Grid Values to Point It takes the Z Value from the DTM and add an attribute to a new pointlayer. <br />The pointlayer is saved as CSV. It gives me a table with x,y and z.<br />And in Spreadsheet I can easily calculate
the length af each vertice and make a sum. :-)<br /><br /><br />Regards<br />Lene Fischer<br /><hr /><br />Sendt: 31. januar 2016 17:52<br />Til: qgis-user<br />Emne: [Qgis-user] Calculating area and length from DTM<br /><br />Hi,<br />Today I have been out collecting data with my GPS in an area with huge differences in heights.<br />My length and area will be from the "flat" area and not accurate/correct.<br /><br />If a contractor should order a fence - it would be too short.... :-O<br /><br />How do I calculate correct when I have the polygon and a terrain model.<br /><br />Regards<br />Lene Fischer<br /><hr /><br />Qgis-user mailing list<br />Qgis-user@lists.osgeo.org<br />List info: <a href="http://lists.osgeo.org/mailman/listinfo/qgis-user">http://lists.osgeo.org/mailman/listinfo/qgis-user</a><br />Unsubscribe: <a href="http://lists.osgeo.org/mailman/listinfo/qgis-user">http://lists.osgeo.org/mailman/listinfo/qgis-user</a><br /><hr /><br />Qgis-user mailing list<br
/>Qgis-user@lists.osgeo.org<br />List info: <a href="http://lists.osgeo.org/mailman/listinfo/qgis-user">http://lists.osgeo.org/mailman/listinfo/qgis-user</a><br />Unsubscribe: <a href="http://lists.osgeo.org/mailman/listinfo/qgis-user">http://lists.osgeo.org/mailman/listinfo/qgis-user</a></pre></blockquote></div><br>
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Sent from mobile. Sorry for being short</body></html>