Fh. Dujardin et al., SMOOTHING TECHNIQUE USING FOURIER-TRANSFORMS APPLIED TO STEREOMETRIC DATA OBTAINED FROM OPTOELECTRONIC RECORDINGS OF HUMAN GAIT, Human movement science, 16(2-3), 1997, pp. 275-282
Stereometric recording on a VICON(TM) optoelectronic system of a contr
olled experimental signal in which the system is used in conditions cl
ose to the real clinical circumstances of a study on gait indicated th
e presence of non-stochastic and non-random errors during the spatial
localization of markers. This observation contradicts a data smoothing
technique using repeated recordings and the computation of a mean sig
nal. The experimental signal corresponded to sinusoidal angular variat
ions of +/- 1 degrees, calculated from the spatial localizations of 4
markers with a sampling frequency of 50 Hz. The mean error for the the
oretical signal was 0.30 degrees, with the maximum reaching 0.91 degre
es. Filtration by Fourier transforms with a cut-off frequency of 10 Hz
made it possible to totally eliminate the raw data noise and to reduc
e the signal error to +/- 0.01 degrees. With this smoothing technique,
variations of the signal velocity and acceleration that were very clo
se to the theoretical values were calculated.