Robust detection, classification and positioning of traffic signs from street-level panoramic images for inventory purposes

Accurate inventories of traffic signs are required for road maintenance and increase of the road safety. These inventories can be performed efficiently based on street-level panoramic images. However, this is a challenging problem, as these images are captured under a wide range of weather conditions. Besides this, occlusions and sign deformations occur and many sign look-a-like objects exist. Our approach is based on detecting present signs in panoramic images, both to derive a classification code and to combine multiple detections into an accurate position of the signs. It starts with detecting the present signs in each panoramic image. Then, all detections are classified to obtain the specific sign type, where also false detections are identified. Afterwards, detections from multiple images are combined to calculate the sign positions. The performance of this approach is extensively evaluated in a large, geographical region, where over 85% of the 3; 341 signs are automatically localized, with only 3:2% false detections. As nearly all missed signs are detected in at least a single image, only very limited manual interactions have to be supplied to safeguard the performance for highly accurate inventories.