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black holes in the dense cloud of a facade

some issues occur when generating dense cloud on facade both using dji phantom 4 pro or autel evo II pro with big holes in facade point cloud (see pic)


the strange thing is that this occurs only on some parts of the point cloud

I tried planning double aerial grid mission with nadir and oblique images with pix4d capture, also adding more images by vertical flight in manual mode…always the same issue.
The same thing occurs with autel evo2 pro and oblique mission with autel explorer app

the overlap from the report appears to be decent

I already tried to process in step 2 switching to 2 minimun number of matching and in step 1 1/2 scale
but with no results

Thanks .

Hi Dellibovi

Welcome to the Pix4D Community!

It seems that the facade’s surface is relatively homogeneous, and it is not possible to create photogrammetry keypoints.
It is possible to change some processing options to get more points in the point cloud, but this will also increase the noise.

Here are some suggestions:

Keep in mind that it is not necessary to modify all those parameters at once. You may be getting better results without changing all the parameters. Note also that processing time might be longer compared when using default values.

If noise is created due to the selected processing options. You can always use PIX4Dmapper to clean the noise: How to edit the point cloud in the rayCloud.

You can find more information here: How to improve the Point Cloud and remove noise.

Please let me know if you are getting better results. I look forward to your response.

Cheers

I followed the given suggestions on another project and these are the results (too many artifact and noise).
Have you any suggestion specific for facade survey?
thankx

Hi dellibovi,

Thank you for the answer and for sharing the picture.
The increase of the noise was expected. if possible, you can always use PIX4Dmapper to clean the noise: How to edit the point cloud in the rayCloud .

Regarding the issue with the facade, it really depends on how you acquired the data. Is the facade visible in your images? Could you eventually share the quality report and some pictures showing this facade?

Cheers

I think the issue is in the projection of other unwanted nearby objects (trees or other buildings)

thanx for the answer

Hi, thank you for the additional information.

In that facade, it is clearly visible that there is almost no texture and for the software, it is almost impossible to find keypoints.

You could try to add planar constraints following the instructions in the next article. It is more suggested for the 3D textured mesh and I can’t guarantee you will get good results, but you can try it.

I also see that you have some points with very different color (image below).

What if you click on one of these points while in the rayCloud? What do you see in the images?

Thank you