[Qgis-user] Calculating area and length from DTM

[Paolo Cavallini]

Thanks Lene. Why not creating a model and adding it to shared repo?
All the best.

Il 1 febbraio 2016 09:33:47 CET, Lene Fischer <lfi at ign.ku.dk> ha scritto:
>Hi Again,
>I have found tree solutions for my problems- Can anyone tell me if they
>are correct.
>
>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.
>
>The second is a Grass function r.surf.area It gives me an area in the
>log.
>
>The functions has a slightly different result, but it´s only 3/1000 :-)
>----------
>
>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. 
>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. 
>The pointlayer is saved as CSV. It gives me a table with x,y and z.
>And in Spreadsheet I can easily calculate the length af each vertice
>and make a sum. :-)
>
>
>Regards
>Lene Fischer
>------------------------------
>Sendt: 31. januar 2016 17:52
>Til: qgis-user
>Emne: [Qgis-user] Calculating area and length from DTM
>
>Hi,
>Today I have been out collecting data with my GPS in an area with huge
>differences in heights.
>My length and area will be from the "flat" area and not
>accurate/correct.
>
>If a contractor should order a fence - it would be too short.... :-O
>
>How do I calculate correct when I have the polygon and a terrain model.
>
>Regards
>Lene Fischer
>_______________________________________________
>Qgis-user mailing list
>Qgis-user at lists.osgeo.org
>List info: http://lists.osgeo.org/mailman/listinfo/qgis-user
>Unsubscribe: http://lists.osgeo.org/mailman/listinfo/qgis-user
>_______________________________________________
>Qgis-user mailing list
>Qgis-user at lists.osgeo.org
>List info: http://lists.osgeo.org/mailman/listinfo/qgis-user
>Unsubscribe: http://lists.osgeo.org/mailman/listinfo/qgis-user

-- 
Sent from mobile. Sorry for being short
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20160201/58377219/attachment.html>