DSM\DTM Warped


#1

Hi,

I’ve generated a DSM+DTM map of a land survey (captured with a Phantom 3 Std + Litchi) using WebODM at default settings.

WebODM completed processing without issue and generated all the required outputs and more, however, upon inspection of the DSM/DTM/3D maps i can see that they have generated incorrectly.

It appears as if the elevation is bowl shaped (which i know is not the case). I have seen a reference to this same anomaly on this Agrobotix FAQ. The FAQ pins the issue ‘on camera or flight setup’ or ‘inaccurate lens calibration’, which i do not believe is the case, as i have also ran the same image set through DroneDeploy and generated an elevation map which looks far closer to the result i was expecting.

Please see below a comparison of the two maps:
comparison

My question is: Have i misconfigured WebODM, or is this a symptom of incorrectly captured images that DroneDeploy is able to correct before processing the elevation map, and, how can i correct this?

Please find below a link to the source images and outputted GeoTIFF files.
https://drive.google.com/drive/folders/1jNfAk2IQiyGQOdPDW69XkPYHXGtq7OcV?usp=sharing

Additional Info:
WebODM is installed natively on Ubuntu Server 16.04 (as recommended by the installation instructions)
Phantom 3 Standard drone is completely stock, no modifications.
No GCPs were recorded or used.
Land area is ~30 acres.

Any help will be greatly appreciated!

Thanks,
Haden.


#2

We don’t perform any barrel distortion correction that you need for phantom 3. Did you calibrate the images before feeding them into ODM?


#3

Related: https://github.com/OpenDroneMap/WebODM/issues/340


#4

No, i was unaware that it was required, therefore did not perform any calibration prior to processing.

I have performed the lens correction using Adobe Lightroom, and am now reprocessing this images.

I’ll let you know what the results are like tomorrow.

Thank you for your time and expertise.

Haden.


#5

A quick update:

I have reprocessed the lens corrected image set, however the results are very much the same.

I can only deduce that the selected lens correction profile in Adobe Lightroom was inappropriate for my images.

I will continue to work on it tomorrow and update the forum with my results for posterity.

Lens corrected source images and outputs have been uploaded to the Google Drive folder.

Once again, thank you.

Additional Info:
Lens Correction settings used were automatically selected by Lightroom based on the image metadata.


#6

You can calibrate with a checkerboard pattern and this: https://github.com/dakotabenjamin/CameraCalibration


#7

Have you found the problem?? I’m having the same issue with a mavic pro, i process in pix4d or drn2map and the issue is gone… but webodm outputs bad dsm/dtms…