Problems with Canopy Height Model

[javicole4]

Hello guys. I´m Javier Hernández from Costa Rica and I´m doing my master thesis with UAV for monitoring forest plantations. I´m working with Pix4D and WebODM. I have noticed that the DSM and DTM generated with WebODM are not as good as those generated in Pix4D. For example, when calculating the canopy height model with the DSM and DTM of WebODM I get a bad CHM (the tree points are not visible and the height results are not correct) but if I do it with Pix4D, I get a good CHM (the tree points are visible and the height result is like the field result). What could be the reason of the problem?

This are the flight parameters:

Flight height= 120m
Front overlap= 80
Lateral overlap= 80
Design= 3D

In WebODM, i used this configuration:
CPU= 3
Memory= 8
Swap= 2,5
Disk size= 64

[javicole4]

I made the flight over a teak plantation.

[Saijin_Naib]

Hey! Sounds like a great project!

Are you able to share your dataset somewhere like dronedb.app and share your full processing parameters?

[javicole4]

Hello, here is the dataset (images of the flight): Hub

I used this Docker configuration:
CPU= 3
Memory= 8
Swap= 2,5
Disk size= 64

In the Web ODM software, I used the option DSM + DTM and didn’t modify anything else.

[Saijin_Naib]

Options: cog: true, crop: 0, debug: true, dem-gapfill-steps: 4, dem-resolution: 1, dsm: true, dtm: true, gps-accuracy: 1, mesh-size: 300000, min-num-features: 16000, orthophoto-resolution: 1, pc-classify: true, pc-ept: true, pc-geometric: true, pc-quality: high, use-3dmesh: true, verbose: true

Is this different from what you’re getting? I seem to be getting acceptable canopy delineation and detail.

Point Cloud looking pretty neat, too!

[javicole4]

I’m going to use this configuration that you mention. And then, compare both projects (with your configuration and the configuration that I used). The main problem was the CHM (Canopy Height Model) that I generate in Qgis, let’s see if that problem disappears with your configuration. I will keep you update. Thanks a lot.