Example of multiple backscatter surveys collected in the same area during different survey cruises using the same MBES (Cook Strait, NZ; the sonar was the EM 300 on R/V Tangaroa). This figure illustrates the discrepancy between the reflectivity by one same MBES along the years. Regardless of the equipment used and the post-processing sequence applied, the overlapping regions should produce a similar image, which is obviously not the case here.