Development and validation of a gyroscope-based turn detection algorithm for alpine skiing in the field

Several methodologies have been proposed to determine turn switches in alpine skiing. A recent study using inertial measurement units (IMU) was able to accurately detect turn switch points in controlled lab conditions. However, this method has yet to be validated during actual skiing in the field. The aim of this study was to further develop and validate this methodology to accurately detect turns in the field, where factors such as slope conditions, velocity, turn length, and turn style can influence the recorded data. A secondary aim was to identify runs. Different turn styles were performed (carving long, short, drifted and snowplough turns) and the performance of the turn detection algorithm was assessed using the ratio, precision and recall. Short carved turns showed values of 0.996 and 0.996, carving long 1.007 and 0.993, drifted 0.833 and 1.000 and snowplough 0.538 and 0.839 for ratio and precision respectively. The results indicated that the improved system was valid and accurate for detecting runs and carved turns. However for drifted turns, while all the turns detected were real, some real turns were missing. Further development needs to be done to include snowplough skiing.