Calibration procedure

General description

For the calibration several images of the calibration corner in room xxx were taken from different viewpoints. Only the two best ones were used (one of them is shown below).

Image of the calibration corner.

The image coordinates of the round targets were measured. For that task the non-round targets were removed from the images. Filtering, thresholding and histogram inversion was done in order to make the targets better visible.

Previous image processed before locating targets.

The mass points of the targets were calculated by weighting the pixel coordinates with the gray values. The labeling of the points was done manually. The calibration calculation was done using cali-program in

Input data

Used input files were:

-DLT2D                 (image coordinates for DLT-calculation)
-DLT3D                 (object coordinates for DLT-calculation)
-IMACRD             (image coordinates for final calculations)
-OBJCRD              (object coordinates for final calculations)
-PHOTOP              (inital values for inner orientation parameters)
-MAPV-control    (control file for calibration calculation)

Computational strategy

The initial values for the orientation parameters were calculated using the DLT. The coordinates of the projection center and rotations of the cameras were solved. Results of this calculation are presented in file MAPV_ANALYSIS_OLD. After that the final calibration was calculated using these initial values. The solved parameters were projection center coordinates, rotations, principal point coordinates, camera constant, affinity, non-orthogonality, three radial terms (powers 3, 5 and 7) and two tangential terms. In the calibration report only projection center coordinates, rotations, principal point coordinates, camera constant, affinity, non-orthogonality and the radial term of power 3 were listed (see calibration report).


The results of the calibration are listed in analysis file MAPV_ANALYSIS. The final calibration parameters were digged out from binary file MAPV_results using a program made by Katri Koistinen. The content of that binary file converted to ascii is in file Because there are two values for each parameter the final values are the averages of these.


The connection between affinity parameter A and x- and y-scales are as follows:x-scale=1+A,y-scale=1-A.