Low and medium frequency synthetic aperture sonar experiments on a rail

The synthetic aperture technique should be among the most important improvements for the next side scan sonar generation. Although the synthetic aperture technique is well known and has been used successfully in radar applications for several decades, only few sonar experiments have been realised. As a consequence of this lack of experiments, synthetic aperture sonar performances are not easy to assess and simulations cannot yet be validated. This paper describes and presents synthetic aperture sonar experiments conducted in GESMA on a 15 m long rail located in a shallow water environment. Data have been registered for a sonar constrained to move on a rail guaranteeing an ideal track so that results can fit well with the theoretical performances (azimutal resolution, echo-to-noise ratio, reverberation-to-shadow ratio, …) and could be used for simulation model validation. Experiments have been realised from low frequency (10 kHz) to medium frequency (80 kHz), for different transmitted signals. The targets were spheres and cylinders and were located along an axis perpendicular to the sonar track at ranges from 15 meters to 50 meters. Some of the targets are partly buried. Detection and classification are discussed. Next a motion compensation algorithm has been used for focusing images obtained with a severe navigation perturbation (a constant 10 degrees yaw) and results are presented