Automatic image analysis of an archery arrow in free flight using high-speed video cameras

Archery at the Olympic games is a competition that hits a target 70 m away. The shooting performance of bows has improved, and athletes are required to have high accuracy shooting at the 10-point zone with a diameter of 122 mm. It is important to know the flight trajectory and attitude of arrow shot to improve the competitive ability. For this purpose, it is necessary to analyze an image of each arrow shot by a high-speed video camera with high accuracy. In this study, an automatic image analysis software for analyzing the velocity and attitude of archery arrows in free flight was developed. In order to confirm the reliability of the analysis results, we measured the velocity and attitude of arrows launched at various initial velocities by a shooting machine using compressed air, and also the arrows shot from bows by an athlete and a robot. Consistency between the results of the conventional visual analysis and those of the automatic image analysis was confirmed. The analysis time was reduced to 1/10 or less. Based on the information obtained from the automatic image analysis, it became possible to examine the flight characteristics of arrow shots, such as the variations in the initial arrow velocity, the initial angle of attack and the velocity decay rate. Knowing these flight characteristics on site will contribute to the optimization of arrow parts composition and the improvement of the athletes’ competitive ability.