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Figure 7.4:
by−real = ay−real ± | ar ∗ cos(θ) |
After acquiring the image coordinates of the field points, the three closest entries
to that point are found from the distortion calibration parameter file. Choosing two
of these three points at a time, two such triangles can be considered. The two points
from the parameter file would correspond to points A and C in the explanation above.
The two triangles considered in such a way give two real world values for point B;
the mean is then calculated to get the final coordinates.
Due to the way the distortion calibration is designed, the distance between two
adjoining points in the calibration grid is 0.1m. Thus cr =0.1 and the equations are
simplified accordingly. →
The reason for approximating over two triangles is that because in the real world
the grid points are located at right angles, however this may not be the case in the
image plane.
From the location of the field points, and thus the corresponding closest points,
the triangle obtained can be classified as follows: Points A, C‘ and C“ are points from