Side scan sonars--Comparison with photographic pictures

The Centre National pour l´Exploitation des Océans (CNEXO - French National Center for Ocean Exploitation) has performed a set of trials with side scan sonars on an artificial lake. This lake was entirely emptied in 1971 and aerial photographs have been taken. So we have reference documents (stereoscopic photo of the bottom and very accurate topographical map) and we can evaluate the sonars by comparison with these documents. Different side scan sonars (50 and 100 Khz) have been tested. In this paper, we give first conclusions from these trials showing comparisons photo-topography-sonar pictures, and submit some reflections about this sensor which is very attractive but must be developed (improvements in stability of fish, signal and data processing, antennas ...).