Relative Mean dB graph

The Relative Mean dB graph is intended for comparing mean dB values on one or more variables that ideally have been recorded in parallel. It is a line plot of normalized sample mean (vertical axis) against variable name (horizontal axis). The sample mean is normalized against a reference variable (the reference value is the sample mean for one of the displayed variables). Alternatively, when no reference variable is set, the graph displays the Mean dB relative to 0dB, for the area of interest on the echogram(s). The Relative Mean dB graph can be linked.

To configure the Relative Mean dB graph, display the Relative Mean dB graph properties dialog box and select the variables to compare.

To display the Relative Mean dB graph from an echogram:

  1. On the View menu, point to Graph, then click Relative Mean dB
  2. Select one or more variables to compare, select a reference variable as required and then click OK
  3. On the Echogram, make a selection or click on a region


  • The echogram window must correspond to one of the variables selected in the Relative Mean dB graph properties box before the graph will update.
  • Place the mouse pointer over a graph point to view the variable identifier (usually the frequency) in the tooltip. X-axis labels use a variable identifier.


Korneliussen, R. and Ona, E (2003). Synthetic echograms generated from relative frequency response. ICES Journal of Marine Science, 60:636-640.

See also

About graphs
About Linking Graphs
Relative Mean dB graph properties dialog box
Frequency Response graph