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Thomas Klein
08-24-2004, 09:51 PM
Dear Biomech-l subscribers,

I'm a sports science student and currently working an my diploma thesis about camera calibration. The objective of my work is to collect several (mainly the most relevant ones) calibration techniques/approaches from the fields of photogrammetry, machine and computer vision, implement them (or use existing freely available implementations) and evaluate them in the context of motion analysis (3D reconstruction).

My purpose is to give a good overview about existing approaches (state of the art) and to describe the posibilities and restrictions (advantages and disadvantages) they provide for the use in motion analysis, with respect to accuracy, efficiency, expenses for setup, volume of calibrated object space (extrapolation issues), use of different calibration targets (planar patterns, 3D patterns, simulated 3D etc., ) and so on. I also want to consider the aspect of applying camera calibration under non-laboratory conditions, which is, as I think, an important fact when using motion analysis for movement analysis in sports.

I have collected an enormous number of publications and literature relating to the subject of camera calibration and selected the following categories, resp. the following representative approaches for further inspection:

A) Linear camera calibration using calibration target

- Standart DLT (originally reported by Abdel-Aziz/Karara)

B) Non-linear approaches using calibration target

- Extended DLT; solving for several parameters modeling lens distorsion (ie. as presented at
www.kwon3d.com)

- Modified DLT version (H. Hatze); Version solving only for the 11 standart DLT-parameters and
extended version taking into account several paramaters for modeling lens distorsion

- R. Tsai's approach solving for 1 additional parameter modeling radial symmetric distorsion

- multi-step methods estimating initial camera parameters by solving linear equations in the first
step and improving these initial guesses by nonlinear optimization within the following steps

C) Camera calibration (ext. orientation) using no calibration target (only scene information) or
corresponding points, whose object-space coordinates are unknown, recieved by waving i.e. a
wand prepared with markers

- Calibrating intrinsic parameters for each camera seperately using i.e. Zang's plane calibration
(Described in: "A flexible camera calibration technique by viewing a plane from unknown
orientation") and afterwards calibate the exterior orientation of the cameras using the intrinsic
parameters and information about corresponding points.

Because my diploma thesis is of course limited to a certain space of time I have not had the chance to go through all available publication in detail. I just want to be sure, that my conception of the existing state of the art is correct and I did not forget to include any important approaches.

I would greatly appreciate any responses pointing out gaps in my concept. Of course I'm also thankful for further suggestiones to take into account witin my work.
As I plan to implement the selected approaches (or use freely available implementations) to test and evaluate them, every available implementation (preferably in c/c++) is wellcome to me, because it will save me some time.

I'm aware of the following existing implementations:

- Fortran DLT implementation by H.J. Woltring
- Tsai Algorith C-implementation by Reg Wilson
- Matlab Camera calibration toolbox by Halir/Bakstein
- MDLT Matlab implementation by Tomislav Pribanic
- Matlab Camera calibration toolbox by Janne Heikkilä

With kind regards,

Thomas Klein


--
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(Frank Outlaw)
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Thomas Klein
Rolandseckstr. 11
81375 München

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