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removing vegetation for volume calculations

i thought i saw Olivier in a webinar remove some vegitation / Trees ,in one of his projects but i cannot find the info on this .Is Pix4D able to remove veg so the ground beneath can be measured in volume ? thanks guys!

You can create a DTM, which is void of tress, objects etc.
Click Process > Run Terrain/Object Point Cloud Classification (beta), then in RayCloud, EDIT the point cloud to move any points left-over from the trees, etc to the DELETED point group. You only want ground points in the TERRAIN Point Group. Un-check all point groups besides TERRAIN to confirm.
Click Process> Generate DTM (beta).
You will have a true DTM to measure volumes.

Thank you so Much for your response !

Does this option eliminates vegetation automatically?

Many thanks!

Carlos,

The Point Cloud Classification does work automatically, but it will leave some vegetation / objects that you will need to move to the DELETED point group manually.   

I assume the newest version does a better job. 

I’m very interested in removing vegetation from our terrains… How can I import the DTM data into C3D? I did a quick search and C3D doesn’t support the DTM format.

Hello again… I’ve gotten to the point of removing vegetation from the point cloud and have generated a 3D textured mesh without the plants. How can I get the contours to generate without plants? I thought the same DSM used for 3D surface would be used for the contour generation?

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Hi David,

You might be looking for this article: https://support.pix4d.com/hc/en-us/articles/203722389
Hope this will help.

Regards,

Thanks! I got it working this morning! BTW, that’s a good link that I was somehow missing in my searches.

Hi,

We have been asked to survey a piece of land which has trees, shrubs, maize crops and grass spread over large parts of it. While we know that majority of the trees and shrubs can be classified as objects, how do we ensure that the maize crops and grass (which can vary in height from 300 mm to 1 meter) can also be classified as objects without ruining the accuracy of the contours generated from the resultant DTM?

Hi Vikshut,

Please find here our procedure about using the point cloud classification tool: https://support.pix4d.com/hc/en-us/articles/203186589

You can adjust the height for detecting objects, meaning everything that is above ground surface.
However, grass cannot be classified as objects if it is too short. You can give it and try and see.
Note the tool is still beta therefore, it might not be very accurate depending on the area.

Regards,

Hi David,

I have the same issue about removing vegetation and importing data into C3D.
Have you solved this problem? Or, you have already figured out the SOP about this issue?
Any suggestions wil help me a lot.

in step 3 check the box where it says DTM and make sure that it says the contour lines will be generated from the DTM but for complex projects you will still need to edit the point cloud by removing vegetation  manually by added the unwanted points to the deleted points and SAVE and rerun step 3.Or in the drop down menue create contour lines then import the project to ArkGis and check the results.

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Hi, Ramiro

Thanks for your quick replying.

I have tried those steps you suggested, but filtering the vegetation points in Pix4Dmapper is an annoying job.
I always got the wrong selecting points.

I still wish Pix4Dmapper could improve this part. I have found the Virtual Surveyor doing that kind job great.

Please see this tutorial video https://vimeo.com/184595503

Editing the point cloud manually is an art it takes patience but with some practice it gets easy. (i actually enjoy it but I’m a nerd)

I watched the video in the link and its pretty cool maybe PIX4D team will apply something similar in the future.

If you select the wrong points exit the point cloud editor and the points wont be added to the deleted.

Thanks, Ramiro

I’ll try your suggestions.