Some pitfalls of short-range standard-target calibration

Abstract

Often it is necessary or desirable to perform a standard-target calibration at rather short range, for example, because of shallow water or interest in measuring animals at short range. A number of general range-dependent effects may prove especially troublesome at short range. These include effects connected with (1) time-varied gain or similar range compensation, (2) finite size of the target, and (3) pulse repetition frequency. The origins of these effects are reviewed and, where particular to a specific system, illustrated by reference to the SIMRAD EK500 echo sounder.