Furuno FSV25S, Operator'S Manual

Page: 41 / 163

2. HORIZONTAL MODE
2-9
2.5 How to Measure Range and Bearing to a Target
Operate the trackball to place the cursor on the target you want to measure the range
and bearing. The range, bearing and depth to the target appear at the upper left corner
of the screen.
Note 1: Trackball position may also be shown in latitude and longitude. For further de-
tails, see page 6-12.
Note 2: The bearing display is available in four formats. See page 6-12.
2.6 How to Eliminate Weak Echoes
Echoes from targets such as bottom and fish return to the transducer in order of dis-
tance to them, and when we compare their intensities at the transducer face, those
from nearer targets are generally stronger due to little propagation attenuation and lit-
tle absorption. If these echoes are displayed directly on the screen, the size of the dis-
played echo from the same school of fish may change with distance, making it difficult
to judge the actual size of the school of fish. To overcome this inconvenience use the
TVG curve function. This function compensates for propagation loss of sound in water;
amplification of echoes on short range is suppressed and gradually increased as
range increases so that similar targets are displayed in the similar intensities irrespec-
tive of the ranges to them.
2.6.1 Change sensitivity of TVG curve
Four TVG curves are available and they vary the gain from large to small.
1. Press the MENU/ESC key to open
the main menu.
2. Click [Gain Setting].
3. Press the
H/V/S key to select the [H1]
or [H2] tab.
Cursor
TRACKBALL DATA
Slant range
Horizontal range
Depth
B Relative or
True bearing
Heading line
Own ship mark
Cursor L/L position
B
34°56.789N
123°45.678E
Gain Setting Quit
H1 P1 H2 P1 V P1
TVG Curve : 15Log
Near Gain : 5.0
Near Gain Distance : 400m
Far Gain : 5.0
Far Gain Distance : 400m
AGC : 5.0
Noise Suppress : 2.0