Camera Model
Principle
The camera model defines the transformation between image space coordinate system and pixel coordinate system.
- Image space coordinate system: The origin is projection center. The Z axis points towards the viewing direction, X axis points to the right, Y axis points down.
- Pixel coordinate system: The origin is the top left corner of the top left pixel. In other words, the coordinates of the top left pixel's center is (0.5, 0.5). The X axis points to the right, Y axis points down.
The notations are described below:
(X, Y, Z) - point coordinates in the image space coordinate system
(u, v) - projected pixel coordinates
(cx, cy) - principal point offset
(K1, K2, K3) - radial distortion coefficients
(P1, P2) - tangential distortion coefficients
(B1, B2) - affinity and non-orthogonality (skew) coefficients
(w, h) - image width and height in pixels
f - focal length
Equations of the transformation are described below :
x = X / Z
y = Y / Z
r = sqrt(x2 + y2 )
x' = x(1 + K1r2 + K2r4 + K3r6) + P1(r2+2x2) + 2P2xy
y' = y(1 + K1r2 + K2r4 + K3r6 ) + P2(r2+2y2) + 2P1xy
u = w * 0.5 + cx + x'f + x'B1 + y'B2
v = h * 0.5 + cy + y'f
LiMapper Internal Parameters File(*.xml)
<?xml version="1.0" encoding="UTF-8"?>
<calibration>
<width>8256</width>
<height>6450</height>
<f>6771.25</f>
<ps>0.00436047</ps> <!-- pixel size -->
<cx>4.57016999999996</cx>
<cy>3.04289000000017</cy>
<k1>-0.0778992</k1>
<k2>0.0695091</k2>
<k3>-0.0223276</k3>
<p1>-2.68206e-5</p1>
<p2>0.000617037</p2>
<b1>6.06111\</b1>
<b2>-0.816488\</b2>
</calibration>