Abstract
Radial and decentring distortion parameters have long been reported as
fundamental elements in camera calibration, especially in digital close range
photogrammetry. This paper reports on an investigation for the determination of both
radial and decentring distortion parameters using analytical plumb-line calibration.
Straight line patterns, ranging from 1, 2, 4, 10 and up to 20 lines, not strictly plumb,
are examined on a set of distorted imagery. Additionally, not only the number of
straight lines but also the linear image distribution is analysed. For that purpose,
linear features have been distributed in different positions and orientations over the
whole of the imagery. Furthermore, the relationship between the parameters
mentioned and the location of the principal point is also analysed, and shows how
sensitive they are to deviations from the centre of the sensor.
The motivation for this paper is the measurement of the minimum number of linear
features for proper calibration of non-metric digital cameras. Both radial and
decentring distortion parameters are examined. Finally, some line patterns are
recommended for making the plumb-line calibration technique a reliable, easy and fast
procedure. Photogrammetrists could use it as a first step in the procedure of camera
calibration; userswho are not experts in photogrammetry could employ it as a final step.
