Agisoft Metashape

Agisoft Metashape => General => Topic started by: TheDroneTeacher on May 05, 2016, 09:15:15 PM

Title: DJI Phantom 3 and 4 Camera calibration parameters
Post by: TheDroneTeacher on May 05, 2016, 09:15:15 PM
Could someone please tell me what the proper Camera calibration parameters are for the Phantom 3 or 4?

fx, fy: Focal length in x- and y-dimensions measured in pixels.
cx, cy: Principal point coordinates, i.e. coordinates of lens optical axis interception with sensor plane.
Skew: Skew transformation coefficient.
k1, k2, k3, k4: Radial distortion coefficients.
p1, p2, p3, p4: Tangential distortion coefficients
Title: Re: DJI Phantom 3 and 4 Camera calibration parameters
Post by: JMR on May 06, 2016, 12:08:42 AM
Here you are: I wouldn't recommend you to use them as fixed parameters at all. In fact I would warn you that a robust Phantom camera calibration is not an easy thing. This otherwise smart drone cameras suffer from severe distortion because of their shutter technology.
Each line of your photos is taken from a slightly different point of view despite of a high "shutter" speed is shown in the EXIF. This fact makes phantoms, inspires, and gopros not very suitable for serious photogrammetry unless you stop on each photo point.
Pix4D has recently implemented a workaround by applying an function that counteracts the expected distortion caused by camera movement.
I guess this undistort function can't cope with all distortion because its distribution will depend on speed and direction of the camera flight path during the time the exposure actually takes, and this information seems to me hard to be known out of the photos but just estimated up to certain limit yet maybe workable.
Alexey has told me that our hero team might pay attention to the issue in future releases, but until this happens you should stop &go while flying or at least avoid doing it much faster than 3m/s while taking photos, otherwise you will get not-so-reliable results with photoscan.
Best regards
GEOBIT
Title: Re: DJI Phantom 3 and 4 Camera calibration parameters
Post by: TheDroneTeacher on May 06, 2016, 04:51:56 AM
Excellent!! I thank you very much.
Title: Re: DJI Phantom 3 and 4 Camera calibration parameters...and phantom 4 pro
Post by: barrubba on March 20, 2017, 10:30:27 PM
..and now that p4pro has mechanical shutter? which are calibration parameter?
a friend working for many year with Ps told me p4pro lens is yet calibrated.
It's true?
Title: Re: DJI Phantom 3 and 4 Camera calibration parameters
Post by: Yoann Courtois on April 06, 2017, 09:46:00 AM
Hi everyone !

No denigration at all but ... :-X
It looks most of you have forget basic rules of photogrammetry:  >:(
- No cameras are calibrate until you have made this calibration, which the fact of measuring internal parameters of your camera: Accurate focal lenth (directly depending on focus), principal point position, distortions
- ONE calibration is proper to ONE camera: Two DJI Phantom 3 cameras don't have the same calibration !!!

And an additional advice for barrubba: Shutter doesn't have influence on calibration, it's only about lens parameters and lens alignment

Regards
Title: Re: DJI Phantom 3 and 4 Camera calibration parameters
Post by: cadm8 on April 06, 2017, 11:16:22 AM
I have to note that I had used Photoscan earlier without any photogrammetric background (just surveying background) and the final product has been exceptional. More now with the rolling shutter correction, aerotriangulation gives you unbelievable results!!
Title: Re: DJI Phantom 3 and 4 Camera calibration parameters
Post by: Yoann Courtois on April 06, 2017, 11:35:13 AM
Yes they are nice !
But depend on your objective, a well-known camera will give us even better accurate model !