Dynamic accuracy survey of the new "single plane--single frame 3-D calibration" technique for use in biomedical applications.

This study tested the accuracy of a new 3-D calibration technique under dynamic situations. The technique was firstly introduced in 1998 for biomechanical human tests and calibrates 3-D volumes in an easy way. It revealed superior in static tests to others. In order to disclose dynamic accuracy two different tests were performed. With this technique it does not matter whether redundant information from multiple camera views is available or not. The mean error for distances measured at 0.018% for redundant information and at 0.012% for the non-redundant test in contrast to other procedures found in literature, which attain values of 0.09% and 0.04% respectively. The maximum error ranged there between 5.5% and 17.9%, whereas the presented data reached values of 0.33% and 0.48%. The more important angle error was at maximum 0.055% (9 times less than the most accurate in literature) and nearly zero for the mean error value. The level of noise was the same in the test with redundancy and 7.4 times lower in the present study than other commercial available systems for non-redundant video information. The new procedure revealed as a stable and very accurate 3-D reconstruction technique for a variety of application not limited to biomedical applications.

A new calibration method for 3-D position measurement in biomedical applications.

Aim of the study was to determine practicality and to test accuracy of a new calibration technique firstly introduced in 1998 by Schmid and Bess for biomechanical human tests. This technique enables three-dimensional calibration of camera positions as well as the calculation of internal and external camera parameters. It can be performed unlike other three-dimensional calibration techniques as the first with a planar calibration grid and only one single video image (of each camera) to calculate all 3-D reconstruction parameters. The tests were performed using two albavision ACAM G-Cameras with a resolution of 480 (h) by 420 (v) pixels. The achievable accuracy of distance measurements in recent commercially available motion measurement systems usually ranges from about 0.09% to 1.77% and higher. Accuracy of 0.0373% was determined with the new calibration technique. The 95% confidence interval ranged at +/- 0.02322 mm, the RMS (root mean square) error at 0.18776 mm. Better accuracy, easier and faster calibration are features of this new calibration technique. Required time for complete calibration ranged below one minute. Anticipating this new method will have good practicality in gait analysis or in research and industry due to increased accuracy and ease of use.