COMPARATIVE ANALYSIS OF TARGET LOCALIZATION ACCURACY IN RADAR PPI IMAGES USING GEOMETRIC ENCLOSURES

Maritime surveillance system requires sensor fusion of radar Plan Position Indicator (PPI) imagery with Automatic Identification System (AIS) data. However, systematic azimuth errors (0°–5°) and irregular echo shapes reduce ship localization accuracy significantly. This study compares three geometric enclosure methods (bounding boxes, convex hulls, and concave hulls) using the publicly available DLR Baltic Sea dataset (X-band, ~10 m resolution, 781 synchronized scans of 4 ships). A 4.5° azimuth offset compensation is applied to minimize target position deviation. Target positions are estimated from calculated bounding box centers and hull centroids from radar images. Validation against AIS ground truth data achieved the lowest average localization errors (58–70 m) for concave hull centroids. It demonstrates up to 12.7% improvement over bounding boxes solution and a 2.1% improvement over convex hulls solution. The results show the accuracy of the concave hulls method in target detection and in preserving echo concavities caused by sea clutter, and noise etc. The concave hull method offers a lightweight and robust solution for real-time Vessel Traffic Services (VTS) and autonomous surface vehicles (ASVs).