Improvement of template matching for distance measurement system based on image sensors

This paper describes an improved template matching for a distance measurement system based on image sensors using a target. Authors have developed the distance measurement system that consists of two movable image sensors for automatic berthing of ships. The measurement system measures a distance by detecting and tracking the target. We aim at applying the distance measurement system for automatic relative positioning system between a ship and a FPSO. In this application, the shape of the target captured in images is deformed by their relative positions and attitudes and then measurements error is increased due to the target deformation. For solving the deformation, we propose an improved template matching robust to target deformation. Improved template matching is able to detect the deformed target with template database which is created by image conversion with perspective projection of a reference template. By using improved template matching, the distance measurement error is decreased. From the experimental results performed in miniature and indoor environments, we confirmed that the measurement error of the relative distance is decreased by using the database.