Furuno NAVNET 1823C - Manual (Page 153)

4. VIDEO SOUNDER OPERATION
4-7
Bottom discrimination display
The bottom discrimination mode displays the bottom echo to help you determine
bottom hardness. A bottom displayed with a short echo tail usually means it is a
soft, sandy bottom. A long echo tail means a hard bottom.
Bottom discrimination display
A-scope display (display only)
The A-scope display, available in all modes, shows echoes at each transmission
with amplitudes and tone proportional to their intensities, on the right 1/10 of the
screen. It is useful for estimating fish species and bottom composition. To turn on
the A-scope display, press the DISPLAY MODE soft key, select display mode
desired, then press the A-SCPE soft key to show “ON” on its label. For modes
other than SINGLE FREQ the screen must be split horizontally to show the
A-scope display.
A-scope display