How correct flag WebODM for high accuracy geotaged images

Hi all!

I’m an Engineer and developer of a PPK system in Brazil for several platforms, mainly, DJI family Drones… but I work with other drones, and platforms (like fixed wings).

Recently I start to use the WebODM to check how the corrections that come from my PPK flow impact the reconstruction in ODM (and possibly indicate to clients).

My Scenario:

Normally I’m using no GCPs (at max 1 to help in f / Z decorrelation), I trust entirely in the image coordinates (that comes from PPK) and some maneuvers in order to help the aerial triangulation to de-correlate properly EO and IO, and provide good self-calibration parameters. It’s is ok and is well-validated and works fine with other programs for 3d reconstruction based on images.

All images processed with PPK flow have EXIF tags indicating high precision. In order to compare, the system works like a DJI Phantom 4 RTK, including the tags and the reached positional accuracy. Then, we can consider that the images were generated with a P4 RTK in RTK mode (high accuracy).

Now, returning to WebODM:

When I creating the project, I can see some parameters related to constraint the perspective center coordinates of the images, like these:

camera-lens:

image

For normal angle cameras, like Phantom 4 Pro, Mavic 2 Pro, it’s a good idea to select “perspective” or “brown”? I understand that brown refer to the Brown-Conrady model, which uses the coefficients: k1,k2,k2,p1,k2… etc … and the option “perspective”, what model/parameters associated?

force-gps:
image

This option should be turned on when high accuracy in image coordinates are present, it’s correct? But I don’t have GCPs in the block, it’s will be unconsidered?

gps-accuracy:

image

Does this option override the EXIF tags with high accuracy? The value for this field is DOP-based?

use-exif:

image ]

Should I check this option to WebODM understand that inside my images there is information for high accuracy positioning?

Well, I’ll appreciate a guideline or tips about my scenario to configure correctly the WebODM, where high accuracy for all images is present.

Thanks for any help or tip!

Thiago Tiedtke dos Reis

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Piero Toffanin may say otherwise, but I would say: make sure your DOP tags are in the images, choose brown, fly a good pattern, and you should be in good shape.

Let us know how it goes!

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Hi,

I’ll use your recommendations! When I finish the processing, I’ll return to share the results!

Thanks!

Thiago T dos Reis

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