Camera calibration is an important step in any photogrammetric process such as ortho-photo or digital elevation model (DEM) production. At Focal Flight, we perform a calibration of each of our vertical cameras on a regular basis and offer calibration service to other aerial photo companies.
Camera calibration maps a lens’s focal length and distortions. This does not change any physical characteristics of the lens, rather it records the existing distortions and exact focal length which are then used by our photogrammetric software.
We have a 4 x 6 meter three dimensional calibration target array. The targets are photographed from 11 different positions in two different orientations. This type of calibration is a “Brown Model” calibration that generates the following parameters to be used by our photogrammetric software.
- C – Calibrated focal length, or principal distance
- XP – Principal point offset in x-image coordinate
- YP – Principal point offset in y-image coordinate
- K1, K2, & K3 – 3rd, 5th, and 7th order term of radial distortion correction
- Coefficients of decentering distortion