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I have a DSM and a DTM in georeferenced TIFF format. I have two shapefiles, one for buildings and one for trees. I want to clip the DSM by both shapefiles separately producing two new files which are then 'superimposed'onto the DTM. therefore I will have a new DSM where it is just buildings and the values of the spaces in between the buildings come from the DTM and then another file for the trees.

Or another way to do it would be to remove the buildings or trees from the DSM and fill in the gaps with the surrounding street level pixel values if this is possible.

After hours of trawling forums I cannot find the answer. Can anyone help? enter image description here

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    Sorry, it isn't totally clear what you are trying to do -- what is the expected output? DSM minus buildings and trees. What have you tried, which software are you using? – John Powell Mar 2 '18 at 15:18
  • I really dont know how to explain it any clearer. In the image top left is a DSM with trees and buildings. I want two new DSMs - one with buildings only and one with trees only. The pixels in the building DSM where the trees used to be should have sensible values such as you would get from the DTM. I have building only and tree only shapefiles to help get to this final output but I dont know how to get there. I am using Arcgis because it is usually a bit more instinctive for me than qgis but I can also use qgis if needs be. – user3390486 Mar 2 '18 at 15:30
  • OK. Well, in my experience, you often get quite unsensible values from DTMs (above the DSM), due to splines, etc, and the inability to observe the ground directly. I have done a lot of this kind of work, but in Postgis. I don't touch ArcGIS with a barge pole, so can't help, I'm sorry. – John Powell Mar 2 '18 at 15:44
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OK I found the solution using QGIS for anyone that is interested.

I performed a Raster>extraction>clipper using the shapefiles as the mask.

Then used the SAGA>Mosaic raster layers tool to merge the clipped DSM with the underlying DTM with 'maximum' chosen as the rule for overlapping areas to ensure the DSM values were superimposed on the DTM.

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