Competitive Swimming Analysis Using CLAS Provided by “Michibiki”

Hiromune Namie, Shunsuke Ishii, Dai Nagafuchi, and Rikimaru Yamada

Abstract:	In this study, we used the Centimeter-level Augmentation Service (CLAS) provided by the Japanese Quasi-Zenith Satellite System (QZSS) “Michibiki” to acquire competitive swimming positioning data and analyzed various parameters such as three-dimensional position, velocity, and acceleration on the basis of centimeter-level positioning accuracy. This swimming measurement experiment was conducted using a CLAS-compatible GNSS receiver, Cohac ? Ten, from Core Co., Ltd., Japan, at the nine-lane 50-m outdoor pool of the National Defense Academy in Yokosuka, Kanagawa Prefecture, Japan. Positioning data were acquired at 100 Hz. While holding a beat board with a GNSS antenna with both hands, a swimmer performed two styles of kicks: the flutter kick and breaststroke kick. Swimming trajectory data were analyzed by comparing CLAS (100 Hz) and postprocessed kinematic GNSS (KGNSS) (1 Hz) measurement data (e.g., carrier phase augmentation correction data) from the Geographical Survey Institute of Japan's Yokosuka GNSS-based Control Station with a baseline length of about 5 km. Regarding the speed of the breaststroke kick, when we compared the same-time data from CLAS and KGNSS, we found that in CLAS, the speed increases rapidly when the feet kick the water. We were able to analyze even the smallest details, such as how the feet were decelerating when pulling back toward the buttocks. Furthermore, when we compared the data obtained from two swimming sessions and analyzed the errors, we found that the average error of the position data in the swimming direction was on the centimeter level. When we analyzed the average speed of CLAS and KGNSS for the breaststroke kick, no error was observed in the speed, but an error of about 20–40 cm/s was observed in the standard deviation. Furthermore, when we analyzed the same-time acceleration, we found that the acceleration suddenly increased when the feet kicked the water during a breaststroke kick. Conventional RTK-GNSS positioning requires the user to prepare a GNSS reference station and a transmission link for augmentation correction data. However, with CLAS, there is no need for individual users to prepare these items. By simply using a CLAS-compatible receiver that costs less than 1,000 dollars, you can access high-precision augmentation correction data for free using GNSS-based control stations, which serve as national coordinate standards.
Published in:	Proceedings of the ION 2024 Pacific PNT Meeting April 15 - 18, 2024 Hilton Waikiki Beach Honolulu, Hawaii
Pages:	402 - 405
Cite this article:	Namie, Hiromune, Ishii, Shunsuke, Nagafuchi, Dai, Yamada, Rikimaru, "Competitive Swimming Analysis Using CLAS Provided by “Michibiki”," Proceedings of the ION 2024 Pacific PNT Meeting, Honolulu, Hawaii, April 2024, pp. 402-405. https://doi.org/10.33012/2024.19645
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