Depth and range are related by the transducer location and orientation.
Depth is a measure of vertical distance below the water surface.
Range is a measure of linear distance from the center of the transducer face.
In the case of a downward pointing vertically oriented transducer Depth = Range + Draft.
Echograms can be displayed in Depth mode or in Range mode. You choose the mode on the Echogram page of the EV File Properties dialog box. The appearance of an echogram will be unaffected by a change of mode, but the reported distance in the toolbar will be affected as will any visible depth/range grid lines and depth/range related analysis variables which are exported.
The depth and range are related as follows:
Depth = Range x Cos(Elevation) + Draft
where:
Draft = Zt - Zw
Zt = Z - vertical offset on the Location page of the Transducer Properties dialog box
Zw = Z coordinate level of the water surface on the Position page of the Platform Properties dialog box
Elevation = Elevation on the Orientation page of the Transducer Properties dialog box
When Elevation is zero, this reduces to the Depth = Range + Draft as described above.
The relationship between depth and range plus transducer geometry as expressed above, can change (while processing in Echoview). The depth is no longer a function of the range and the transducer geometry when a Beam Select virtual variable is created from a multibeam variable. In this case, the depth/range relationship is worked out internally using the angle of the selected beam. Further information about beams in multibeam echograms can be found in the About sector plots and beams.
About single target depths
About transducer geometry
About draft
Calculating range and depth from exported data