Beyond the Carving-Skidding Dichotomy: Sensor-assisted Measurement of Angle of Attack in Skiing
Christoph Thorwartl, Sebastian Schütz, Helmut Holzer, Bernd Resch (2025): Beyond the Carving-Skidding Dichotomy: Sensor-assisted Measurement of Angle of Attack in Skiing In: Proceedings of 10th International Congress on Science and Skiing
INTRODUCTION: A carving turn is defined by the ski experiencing minimal to no lateral movement relative to its path. Divergence between the ski’s orientation vector (E) and the resultant velocity vector (v), known as the angle of attack (AoA), results in skidding. Reid et al. (2020) investigated the AoA in the field using a videographic method, but this approach was laborious [1]. Up to now, only Schütz et al. (2024) have reported a sensor-based solution, but it was tested solely in the lab, without field data [2]. Therefore, this study aims to evaluate a sensor-based solution for detecting AoA in the field and distinguishing between carving, parallel ski steering, and transitions.
METHODS: Four IMUs (Xsens DOT) and a GNSS (Xsens, MTi-680G) were equipped to the ski (Atomic Redster G7, length: 1.82 m, radius: 17.3 m) with the antenna of the GNSS sensor placed directly on top of the GNSS sensor. The participant carried a backpack with a laptop to connect to the GNSS and performed 20 turns of each of the following: (i) carving, (ii) parallel ski steering, and (iii) transitions from parallel ski steering to carving. To address distortions in v data during skiing, a three-step filtering process was applied separately to each dimension: (i) Kalman smoothing, (ii) Hampel filtering for outlier removal, and (iii) Butterworth low-pass filtering. The AoA was subsequently calculated using the procedure outlined in previous research [2]. The runs were divided into individual turns using gyroscope-based turn detection in accordance with Martinez et al. (2019) [3]. The right turns (instrumented outer ski) were time-normalized, and the mean AoA ± standard error (SE) was calculated for each technique.
RESULTS/DISCUSSION: The results indicate that carving has the lowest mean AoA of 6.26°, while parallel ski steering has the highest mean AoA of 18.80°. The peak AoA for parallel ski steering is 32.47°, and the minimum AoA for carving is 4.09°. This is in line with past research, showing that the AoA increases as skidding is introduced [1]. During the transition, the maximum AoA of 22.13° is reached at approximately 20% of the turn completion, after which it decreases. This observation aligns with the video data, which clearly shows a transition from a skidding to a carving turn. In summary, each skiing technique can be associated with a distinct progression of the AoA during a turn.
CONCLUSION: Given that the AoA examines the definition of carving, the authors consider it crucial for monitoring and improving performance. Tracking AoA gives coaches and athletes insights to refine technique and make data-driven adjustments for better skiing proficiency.
