Setting manual camera parameters in json file

Svallone · 17 March 2023 15:16

Hi!

Thanks for the great WebODM!!

Does anybody want to help in manually setting up the .json file with the camera parameters in webodm?

Specifically, the cameras are the Mapirs. I’m working on a parallel project in metashape and in WebODM and from the use of metashape, I already know that the camera parameters have to be set in order to get accurate results, otherwise DEM and point cloud would be bent and have a dome effect, as already described by others.

I learned how to set those parameters in metashape, but I couldn’t find any info about this setting in WebODM.

Could you at least point to a working .json file?

Camera parameters of the mapirs can be found in here

Thanks!!!

Saijin_Naib · 17 March 2023 15:26

Welcome!

OpenSFM has a file for that here:

github.com

mapillary/OpenSfM/blob/main/opensfm/data/camera_calibration.yaml

[{
    "gopro":{
        "MODEL":{
            "hero8 black":{
                "focal_x": 0.47720253548498875,
                "focal_y": 0.4776476227437118,
                "k1": -0.004417272934201867,
                "k2": 0.0026456102958567146,
                "c_x": -0.0017664444590190724,
                "c_y": 0.006393052002726844,
                "p1": 0.0, "p2": 0.0, "k3": 0.0,
                "projection_type": "brown"
            }
        },
        "FOCAL":{
            # GoPro Hero 3, 7MP medium
            20: {"focal": 0.625, "k1": -0.37, "k2": 0.28},
            # GoPro Hero 3, 7MP wide
            15: {"focal": 0.466, "k1": -0.195, "k2": 0.030},
            # GoPro Hero 2, 5MP medium

This file has been truncated. show original

Do you have all those MapIR cameras on-hand? We’d love to collect the Rolling Shutter data for them, too :

Svallone · 17 March 2023 17:53

Hi!

Thanks for the super fast reply and for pointing to that resources.

I actually have three of them RGN, RE and RGB (survey3N, sorry I didn’t specify).

I will try my best to calculate the rolling shutter after recovering a ~2khz Led somewhere, but I cannot promise much, even if it would be very interesting to know.

I also have a new Mavic 3 M that will be our first drone. I can’t tell yet for sure, but from the few released info (see second table here) it seems that the single band cameras are rolling shutter too. I will try to collect more info on that too and, in the case, calculate rolling shutter speed even for those sensors.

Saijin_Naib · 17 March 2023 18:41

Awesome! Any assistance we can get to gather camera data is a huge help, since we can support the corrections for more people!

I personally (developed) and tested the No-Tinker method using just a Raspberry Pi Pico, which I found to be easier to source and use than making a breadboard (though simple if you have the stuff already).