A multi-perspective ensonification method comprising the steps of: installing a multibeam echo sounder system, MBES, (100; 102) on a water going vehicle such that plural transducers in a single MBES projector array and plural transducers in a single MBES hydrophone array are in a Mills Cross arrangement; modeling a waterbody with a plurality of "j" superposed layers (l 1 ... l j ) having respective layer thicknesses (t 1 ... t j ), each of the j layers having a layer entry sound speed and a layer exit sound speed such that a set of (j+1) sound speed values (c 1 , c 2 ... c j+1 ) characterize the sound speed profile through the layers; designing a vehicle route and traversing the route such that during MBES operation along the route i) plural primary areas are ensonified, ii) plural secondary areas are ensonified, iii) each primary area is overlapped by a respective secondary area, and iv) for each overlap a first echo originating therein traverses a first path to the MBES at a first location and a second echo originating therein traverses a second path to the MBES at a second location different from the first location; via a travel time corresponding to each echo, modeling the propagation of sound through the waterbody to locate in three dimensions a reflector that returned the echo; one of the dimensions indicating a waterbody depth and the other two dimensions indicating coordinates in a reflector plane parallel to the waterbody free surface; selecting a colocation metric and using the metric to identify groups of reflectors that are colocated in the reflector plane; for each group of colocated reflectors, quantifying disagreements in the waterbody depths corresponding to the reflectors in the group; and, determining a set of adjusted sound speed values that tends to simultaneously reduce the disagreement within each group of depth estimates. installing a multibeam echo sounder system, MBES, (100; 102) on a water going vehicle such that plural transducers in a single MBES projector array and plural transducers in a single MBES hydrophone array are in a Mills Cross arrangement; modeling a waterbody with a plurality of "j" superposed layers (l 1 ... l j ) having respective layer thicknesses (t 1 ... t j ), each of the j layers having a layer entry sound speed and a layer exit sound speed such that a set of (j+1) sound speed values (c 1 , c 2 ... c j+1 ) characterize the sound speed profile through the layers; designing a vehicle route and traversing the route such that during MBES operation along the route i) plural primary areas are ensonified, ii) plural secondary areas are ensonified, iii) each primary area is overlapped by a respective secondary area, and iv) for each overlap a first echo originating therein traverses a first path to the MBES at a first location and a second echo originating therein traverses a second path to the MBES at a second location different from the first location; via a travel time corresponding to each echo, modeling the propagation of sound through the waterbody to locate in three dimensions a reflector that returned the echo; one of the dimensions indicating a waterbody depth and the other two dimensions indicating coordinates in a reflector plane parallel to the waterbody free surface; selecting a colocation metric and using the metric to identify groups of reflectors that are colocated in the reflector plane; for each group of colocated reflectors, quantifying disagreements in the waterbody depths corresponding to the reflectors in the group; and, determining a set of adjusted sound speed values that tends to simultaneously reduce the disagreement within each group of depth estimates. <EOS>