Two scatterers at similar range give an echo which may appear to be du
e to a single scatterer. Methods for determining target strength that
depend on resolving single scatterers may fail in this instance. Stati
stics associated with the described special case of coincidence are de
rived and illustrated by theoretical computation for the SIMRAD EK500
echo sounder system with the ES38B split-beam transducer resonant at 3
8 kHz. Connections to angle measurement in radar and swath bathymetry
and to bottom-scattering-strength measurement are noted. (C) 1996 Acou
stical Society of America.