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 malppari@hut.fi.
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).
Results
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 map1.cam.
Because there are two values for each parameter the final values are the
averages of these.
Notes
The connection between affinity parameter A and x- and y-scales are as
follows:x-scale=1+A,y-scale=1-A.