A Computer Vision Approach to Automatically Measure the Initial Spin-Rate of Artillery Projectiles Painted With Stripes

High-speed video has been used by ballistics engineers as a cost-effective technique to measure the spin-rates of both spin-stabilized and fin-stabilized artillery projectiles. Often at test ranges, state-of-the-art video systems are used to verify critical launch events following muzzle exit. From manual analysis of these videos, important performance metrics such as velocity, pitch angle, and spin-rate can be estimated. To do this, operators step through the video frames and record the time at which certain fiducial markings or numbered stripes are observed on the projectile as it rotates. The different methods evaluated in this paper are automated processes for calculating the muzzle-exit spin-rate from launch videos of spin-stabilized artillery projectiles painted with stripes. Image processing and computer vision techniques are employed to segment the shape of the projectile and extract the stripe pattern in each video frame. The most accurate algorithm estimates are validated to within 0.02 % for both laboratory and computer-simulated flight video and within 0.13 % for manual analysis of real flight video. The sensitivities of the methods to image resolution, video frame-rate, and the length of flight captured are evaluated. Areas of continued research and recommendations for increasing the accuracy of measurements in future tests are also identified.