Urban scene understanding is an active area of research. Devoid of any context, entrance detection in outdoor scenes is extremely challenging. Scene clutter is a problem because entrances typically make up only a small portion of the image of a building facade. Most entrances have doors whereas some do not. Moreover, there is a wide variety of sizes and appearances of doors. Arches over doors, steps leading up to doors, transparent doors, reflective doors, doors with large handles, partially open doors, shuttered doors etc., lead to large intra-class variation. Additionally, the camera view, occlusions due to trees, vehicles, people, and other objects in the scene further complicate the entrance detection task.
USPTO Backgrounds
USPTO Backgrounds