A method to minimise error in 2D-DLT reconstruction of non-planar markers filmed with a moving camera.
This article describes a method that allows estimating, with the 2D version of the direct linear transformation (DLT), the actual 2D coordinates of a point when the latter is not strictly in the calibration plane. Markers placed in vertical line, above, below and in the centre of a horizontal calibration plane were filmed by a moving camera. Without correction, strong errors (up to 64.5%) were noticed for markers out of the calibration plane. After correction, calculated coordinates were consistent with actual values (error < 0.55%). The method was then applied to slip distance measurement, using a marker fixed on the hoof of a horse trotting on a calibrated track while being followed with a camera. The correction effect represented 6.6% of slip distance. Combined with the 2D-DLT transformation, the proposed corrective method allows an accurate measurement of slip distances, for high-speed outdoor locomotion analysis, using a moving camera.
a Université Paris-Est, Ecole Nationale Vétérinaire d'Alfort , USC BPLC 957, Maisons-Alfort , F-94704 , France.
Laurène
L
Holden-Douilly
Philippe
P
Pourcelot
Henry
H
Chateau
Sylvain
S
Falala
Nathalie
N
Crevier-Denoix
D000465:Algorithms; D000818:Animals; D002138:Calibration; D006724:Hoof and Claw; D006736:Horses; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008124:Locomotion; D010781:Photography / Q000295:instrumentation