creating DTM from TLS pointcloud with "minimum height" function

[Brahm]

Hi there,
I want to create a DTM from my TLS pointcloud (with point density of 10cm). So I was first separating the vegatation from the ground by CANUPO, which worked quite well, but there a of course still mistakes. Afterwards I used the "rasterize tool" to create a new pointcloud by applying the "minimum height" function on the points. I used different step (resolution) for Vegetation and ground, a smaller one for ground, a larger on for vegetation. I tried different variations of steps (0.1m; 0.25m, 0.5m; 1.0m) but I still don`t know, which is the best to work with. If I use a small step, the cloud is still very dense and very time consuming for deleting the wrong points. using a larger step, information gets lost.

So could anyone please share his experience with me and recommend a good step for Vegetation and ground?

In the resulting pointcloud I would use for deleting wrong points and use it as input for rastering the DTM afterwards.

Thanks Brahm

[daniel]

Have you tried qCSF by the way? http://www.cloudcompare.org/doc/wiki/in ... F_(plugin)

[Brahm]

HI Daniel,
thank you for your fast reply. No, I havent used CSF yet, but as I red in a comment from you, it should yield a quite similar result like CANUPO, which i appled in several variations. And if I used CSF, I still would have to clean the pointcloud afterwards by deleting Points. So do you have any experience with the best resolution (step) for this purpose (in TSL pointcloud) for the "Minimum height function" in the "rasterize tool" (one for ground/ one for Vegetation)?

thank you ciao Brahm

[daniel]

qCSF tends to generate much cleaner clouds 'by design'. I don't think one need to clean it afterwards.

Otherwise, it's hard to tell for the right 'resolution', as it mainly depends on your clouds density. And it's a quite simple way to address this problem, therefore I wouldn't expect a too much detailed result.

[Brahm]

Hi Daniel,
thanks. Ok, qCSF sounds interesting...!

Of course principially finding the best resolution is simple. But since there are many resolution-combinations possible between vegetation and ground, it is a long trial and error process, that will lead to the best combination .... so if anyone has some experience, it could be usefull,

thank you Brahm

[Brahm]

Hi Daniel,
I tested cCSF according to your advice, but unfortunately I have to tell you,that it did not work at all in steeper areas (rocks), although I tried with all the different Scenes options. The flatter areas I did not check...

ciao Brahm