Messages

1

Camera Calibration / Re: How to calibrate a UAV camera in Metashape 1.5.1!!!

« on: March 17, 2019, 03:43:58 PM »

try this workflow https://de.mathworks.com/help/vision/ug/single-camera-calibrator-app.html … i use it for every lens …concerning color … there is a bunch of LUTs out there for any camera you own.
regards nj

2

General / Re: When to use camera calibrate function?

« on: September 22, 2014, 03:25:26 PM »

When to use camera calibrate function?
Is there any criteria for when this should be used? And at what stage?

certain scenarios will require camera calibration.
recently i tested a mirror-less system with a zoom-lens, fixed @ the max. fov.
i took about 10 photos of a flat, well textured brick-wall. camera-orientation close to the normal case, like in aerial or stereo photogrammetry.

the reconstuction without pre-calibration resulted in a (barrel-like) distorted model. the wall was bent. the reconstruction with data from calibration resulted in an accurate model.
there are many articles out there, examinating the process of self-calibration.
like cahngchang wu's paper: Critical Configurations For Radial Distortion Self-Calibration http://ccwu.me/file/radial.pdf or a german publication presenting charts of deviation of parameters from self-calibration vs. calibrated data. https://www.hcu-hamburg.de/fileadmin/documents/Geomatik/Labor_Photo/publik/dvw_schriftenreihe_tls2012_remondino_kersten.pdf

you should apply the calibration-profile before you start image alignment.

3

General / Re: limit of accuracy by pixelpitch

« on: September 11, 2014, 01:28:31 AM »

If you can't resolve it on the sensor, you can't resolve it in the image

sure, for a single spot, but what happens at an edge (perfect geometrical intersection of two surfaces) ?
the exact geometric information of that edge would get lost but the intersection of this surfaces ( different shades ) would still be there and visible on the pictures … given the stated example of 1mm accuracy … one couldn't fulfill this demand of accuracy?!

4

General / limit of accuracy by pixelpitch

« on: September 11, 2014, 12:13:33 AM »

is it correct that the pixelpitch determines the smallest feature detected on an image?

given an image scale of 1:200 and a desired accuracy of 1mm, this millimeter will be 5micron on the sensor. if the pixelpitch of the camera is larger than 5 micron would the claim to accuracy of 1mm still be given ?

what defines the limit of accuracy concerning resolution? … if all conditions and specs of optics, light geometry and texture would be just ideal?