On the influence of positioning errors on tomography - based sonar imaging systems

The receiver signal of sonar systems consists of the sum of reflected signals stemming from many scatterers. The resolution of sonar imaging systems depends in range direction on the bandwidths of the transmitter signal and in angular direction on the beamwidth of the receiver antenna. Tomography is a very promising method to improve the resolution of such sonar systems in angular direction. Basically, tomography relies on an appropriate fusion of sonar images of a scene derived from different spatial positions and thus under different viewing angles. Obviously, knowledge of the exact antenna position during acquisition of the different basic images is substantial for achieving high quality tomography reconstructions. Positioning errors, i.e. differences between real antenna locations and assumed (measured) antenna positions, causes blurring of the reconstructed image of the scene. In this paper the aforementioned image degradations are demonstrated by means of simulation results. Furthermore, basic ideas to reduce the problems caused by positioning errors are presented for a forward looking sonar with tomographic signal processing.