Furuno CH-250 - Manual (Page 41)

2-23
2.14 Interpreting the Horizontal Display
This section provides information necessary for interpreting the horizontal display.
2.14.1 How the horizontal mode picture is painted
The wide sounding beam is emitted from the soundome at a certain tilt angle (see hatched area
in the figure below). The information (target echoes) obtained by this beam is displayed in
sectors of increments of 12
°
of the screen. Thus, all directions around the boat are sounded in
30 times of transmissions.
Note: When the “FAST SCAN” is switched off, the equipment operates in a narrow sounding
beam. Then, the echoes appear on a 6
°
sector in each transmission, so 60
transmissions are required to complete the full 360
°
picture (6
°
x 60=360
°
). This means
that training speed is slower. However, since transmission power is concentrated into the
narrow sounding beam, a superior detection range is obtained. Furthermore, since the
bottom contour is painted distinctly, bottom fish may be more easily detected.
Sounding Beam Screen Display
Tilt:
θ
Sounding
Beam
Tilt:
θ
Train: 6˚*
When the narrow sounding beam (6˚)
is selected 60 transmissions are required
to complete the full circle.
*12˚ When high speed training is
selected.
Figure 2-20 How the horizontal mode picture is painted