Visualizing Skiers' Trajectories in Monocular Videos

Trajectories are fundamental to winning in alpine skiing. Tools enabling the analysis of such curves can enhance the training activity and enrich broadcasting content. In this paper, we propose SkiTraVis, an algorithm to visualize the sequence of points traversed by a skier during its performance. SkiTraVis works on monocular videos and constitutes a pipeline of a visual tracker to model the skier's motion and of a frame correspondence module to estimate the camera's motion. The separation of the two motions enables the visualization of the trajectory according to the moving camera's perspective. We performed experiments on videos of real-world professional competitions to quantify the visualization error, the computational efficiency, as well as the applicability. Overall, the results achieved demonstrate the potential of our solution for broadcasting media enhancement and coach assistance.

1. Introduction

Due to the popularity of alpine skiing [60], the competitive form of such a sport discipline is one of the most important markets of the winter sports industry [12]. The international regulations of alpine skiing competitions [54] require the definition of a path of so-called turning gates down a hill. Differing in the overall length of the course and in the distance between the gates, four popular alpine skiing sub-disciplines are present nowadays: Slalom (SL), Giant Slalom (GS), Super-G (SG), and Downhill (DH). In each of these, the winning goal is the same: ski down through the gates of the designed course in the shortest time possible.