Automated Ski Velocity and Jump Length Determination in Ski Jumping Based on Unobtrusive and Wearable Sensors

Abstract

Although ski jumping is a widely investigated sport, competitions and training sessions are rarely supported by state-of-the-art technology. Supporting technologies could focus on a continuous velocity determination and visualization for competitions as well as on an analysis of the velocity development and the jump length for training sessions. In the literature, there are several approaches for jump analysis. However, the majority of these approaches aim for a biomechanical analysis instead of a support system for frequent use. They do not fulfill the requirements of unobtrusiveness and usability that are necessary for a long-term application in competitions and training. In this paper, we propose an algorithm for ski velocity calculation and jump length determination based on the processing of unobtrusively obtained ski jumping data. Our algorithm is evaluated with data from eleven athletes in two different acquisitions. The results show an error of the velocity measurement at take-off of (which equals -3.0 % ± 4.7 % in reference to the estimated average take-off velocity) compared to a light barrier system. The error of the jump length compared to a video-based system is 0.8 m ± 2.9 m (which equals 0.9 % ± 3.4 % of the average jump length of the training jumps in this work). Although our proposed system does not outperform existing camera-based methods of jump length measurements at competitions, it provides an affordable and unobtrusive support for competitions and has the potential to simplify analyses in standard training.

Ski Jumping Trajectory Reconstruction Using Wearable Sensors via Extended Rauch-Tung-Striebel Smoother with State Constraints

“…The magnetometer provides triaxial local magnetic field flux density measurements also at 100 Hz. To the best of our knowledge, the IMU and magnetometer sensor chips in the iPhone 7 provide raw measurement data with a similar accuracy level as previous studies, e.g., [2,4,6,8]. The raw data measured by the smartphone was logged via the application Phyphox [12] and was attached to the jumper's right upper arm using a running armband with the orientation shown in Figure 1.…”

“…Traditional solutions to meet this demand are video analysis techniques based on camera recorded videos [1]. However, such a system has the disadvantage that it generally only covers limited parts of the jumping area [2]. To record the entire jump, a large number of cameras would be required making the system expensive and hard to calibrate.…”

“…Chardonnens et al [4] presented an IMU-based system measuring ski jumping dynamics including the position and velocity of the center of mass perpendicular to the table during take-off. Groh et al [2] proposed a measurement system with IMUs and a light barrier to estimate the ski velocity and jump length. Blumenbach [5] designed and tested a helmet with a high-precision Global Positioning System (GPS) receiver for the positioning of ski jumpers.…”

Performance Analysis in Ski Jumping with a Differential Global Navigation Satellite System and Video-Based Pose Estimation

“…Therefore, in recent years, wearable sensors that allow coverage of the entire process from start of the in-run to the landing have been used. Most commonly, inertial measurement units (IMUs) have been used to measure both kinematics and kinetics with promising results [ 4 , 26 , 27 , 28 , 29 , 30 , 31 ]. The shortcoming with IMU measures is that accuracy can be questionable when estimating position integrated from acceleration measures [ 8 ].…”

Ski Position during the Flight and Landing Preparation Phases in Ski Jumping Detected with Inertial Sensors

“…The potential of the use of inertial sensors placed only on the skis to detect their position has been introduced and tested on one subject by Kreibich and colleagues [8]. Always with the sensors placed on the skis, Groh and colleagues [22] were able to detect the ski speed and the jump length. Moreover, the same author introduced the use of inertial sensors on the skis to detect the angular momentum during landing, validating it with custom-made force-measuring bindings [23].…”