Development of image sonar simulator for underwater object recognition

In this paper, two preliminary basic studies of underwater recognition are reported: modeling an image sonar and developing its simulator. The display mechanism of the image sonar is analyzed, and an image sonar model is proposed. The image sonar emits ultrasound beams in the forward direction and then detects those that strike objects and are reflected from their surfaces. The ultrasound beams are modeled as a set of rays, and the image sonar is modeled as an object emitting the rays at a certain position and orientation. The surface of the objects to be observed is modeled as consisting of many small polygons so that any arbitrary shape can be represented by these polygons. Collisions between the ultrasound beams and objects are described in terms of the points at which the rays intersect the polygons. On the basis of the model, a simulator for the image sonar is developed. The sonar images made by the simulator are compared with real sonar images to confirm the validity of the model.