Combining Short and Wide Baseline Stereo Cameras for Improved Maritime Target Tracking*

Target tracking is essential for autonomous vehicles to avoid collisions. Using a stereo camera for the target tracking gives a dense representation of the targets, contrary to the the sparser data on typical radars and lidars. With a wider baseline stereo camera the depth measurements are more accurate, but the stereo matching challenge is greater, especially in the maritime domain with reflections on the water. Earlier classical methods of tracking using stereo cameras have often tracked targets by first doing water surface estimation and then finding objects perturbing the plane. The challenge is then to get a good estimate of the water surface plane while still having precise measurements to the targets. We propose both a short baseline method and a multi-baseline method for target detection. The multi-baseline method uses a short baseline stereo camera to find the water plane and uses a wider baseline stereo camera to get accurate target measurements. The targets are consistently being tracked when using data collected during the summer of 2023 from an autonomous ferry prototype compared to ground truth GNSS tracks. The short baseline method achieves minimal error for a day cruiser boat 40 m away using a camera baseline of only 12 cm. The multi-baseline method further improves the accuracy of boat measurements, especially for a far-away small kayak.