Analysis of video‐recorded images to determine linear and angular dimensions in the growing horse

Abstract

Summary Studies of growth and conformation require statistical methods that are not applicable to subjective conformation standards used by breeders and trainers. A new system was developed to provide an objective approach for both science and industry, based on analysis of video images to measure aspects of conformation that were represented by angles or lengths. A studio crush was developed in which video images of horses of different sizes were taken after bone protuberances, located by palpation, were marked with white paper stickers. Screen pixel coordinates of calibration marks, bone markers and points on horse outlines were digitised from captured images and corrected for aspect ratio and ‘fish‐eye’ lens effects. Calculations from the corrected coordinates produced linear dimensions and angular dimensions useful for comparison of horses for conformation and experimental purposes. The precision achieved by the method in determining linear and angular dimensions was examined through systematically determining variance for isolated steps of the procedure. Angles of the front limbs viewed from in front were determined with a standard deviation of 2–5 degrees and effects of viewing angle were detectable statistically. The height of the rump and wither were determined with precision closely related to the limitations encountered in locating a point on a screen, which was greater for markers applied to the skin than for points at the edge of the image. Parameters determined from markers applied to the skin were, however, more variable (because their relation to bone position was affected by movement), but still provided a means by which a number of aspects of size and conformation can be determined objectively for many horses during growth. Sufficient precision was achieved to detect statistically relatively small effects on calculated parameters of camera height position.

Variation in frontal plane joint angles in horses

“…Quantitative methods of conformation and gait assessment have since been developed, that allow evidence‐based assessment of conformation. Initially, these involved tape measures and goniometers, then photography (Kronacher and Ogrizek 1931) and videography (Hunt et al . 1999), later superseded by motion analysis systems (Weller et al .…”

“…Quantitative methods of conformation and gait assessment have since been developed, that allow evidence-based assessment of conformation. Initially, these involved tape measures and goniometers, then photography (Kronacher and Ogrizek 1931) and videography (Hunt et al 1999), later superseded by motion analysis systems (Weller et al 2006c). The use of motion analysis over photography and videography resolves geometric errors associated with the acquisition of 2-dimensional (2D) images from 3D structures, and is independent of camera position relative to the horse (Weller et al 2006c).…”

Reliability of conformational measurements in the horse using a three-dimensional motion analysis system

“…These parameters are usually measured from the external appearance of an animal or, less commonly, on radiographs (Barr 1994;Eksell et al 1998). In early studies, measurements were performed with a tape measure and a goniometer, a time-consuming process eventually replaced by photography (Kronacher and Ogrizek 1931;Magnusson 1985;Holmström et al 1990) or video-recorded images (Hunt et al 1999). In most recent studies, digital photography was employed with (Dressel 2002) or without (Anderson and McIlwraith 2004) a reference frame.…”

Curvas ângulo-tempo das articulações dos eqüinos marchadores

“…As imagens foram digitalizadas utilizando-se o programa Simi-Motion 3D, 6.0 (Simi, 2004) empregando-se a metodologia de análise dos ângulos por meio de imagens conforme sugeridas por Mota (1999) e Hunt et al (1999). Os ângulos analisados foram: inclinação da escápula com a horizontal, inclinação do braço com a horizontal, ângulo escapuloumeral, ângulo úmero-radial, ângulo do carpo, ângulo coxo-femoral, ângulo femorotibiopatelar, ângulo tibiotarsicometatársico.…”