CloudCompare forum

Based on this previous question http://www.cloudcompare.org/forum/viewt ... 7&start=20 to work through generating a DTM, I am unable to proceed to subtract DTM from non-ground points (vegetation) to get height. How can I do this, is there an inbuilt function for subtraction?

I also exported (using file>save option) data (non-ground, ground points etc) for further analysis. When I view this data in ArGIS it only shows null values. How do I export a valid dataset.

To filter ground from non-ground points I used the CFS algorithm. However, my dataset has several classes in the non-ground point data which I need to remove so that I can only keep non-ground points belonging to vegetation? How to do this with several las files? (note, I tried using CSF in python but there is memory issue).

An urgent feedback will be appreciated. Thanks.

For DTM subtraction, you can select the ground points and the non-ground points, and then use the 2.5D Volume calculation tool to compute the difference between the 2 rasters (see https://www.cloudcompare.org/doc/wiki/i ... .5D_Volume - the documentation may not be up-to-date, but it's possible to export the resulting grid as a cloud).

To which format are you exporting the files?

To select the points based on their classification value, you'll have first to select the 'classification' scalar field on each cloud separately (probably the worst part). Then you can select them all and use the 'Edit > Scalar fields > Filter by Value' tool. You can also automate that process with the command line tool (especially with the latest 2.13.alpha version, that allows the user to select scalar fields by their name).

Daniel,

Thank you for your feedback.

Unto the question, 'To which format are you exporting the files?'
I am exporting as a point cloud. I wish to maintain the original values.

I understood it was a point cloud, but which file format? (LAS maybe?)

Daniel,

Yes, as a las format. I am not sure why I can only export as raster, .tif, if am not mistaken?

Hum, so if you use the Rasterize tool, then you can indeed only export to geotiff (that's a current limitation of this tool).

And if you want to export the ground points obtained with the CSF plugin, I still don't see the issue, as you should get a subset of the original cloud (with all the right scalar fields, etc.). Are you using an old version of CC maybe? Can you try with the latest 2.13.alpha version?