How To Read Images; Reflections From The Sea Bottom; Å Reading Topographical Features Of The Sea Bottom; Reading Geological Features Of The Sea Bottom - Icom FP-561 Instruction Manual

16
rSOUNDER MODEq HOW TO READ IMAGES
(16)-1 Reflections from the
sea bottom
Å Reading topographical features
of the sea bottom
Flat terrain
GPS
H
315 T
ı Reading geological features of
the sea bottom
GPS
H
315 T
Soil/sand
57
Reflections from the sea bottom are displayed in red provided that the sen-
sitivity is properly set (
Screen images of the sea bottom provide you with information on the topographi-
cal and geological features of the sea bottom. Such information will help you
search for good fishing banks.
Submarine terrains may be flat or hilly, just as is the case with land.
On screen images, topographical features of the sea bottom are displayed,
as in:
Topographical feature
Hilly terrain
48 21.417N 125 26.643W GPS
0
20
40
60
80
100
H
58.4
10.2KT 58 F
315 T
FT
On screen images, geological features of the sea bottom are displayed, as in:
Geological feature
Hard
48 21.417N 125 26.643W
(e.g., rock, coral reef)
0
Soft
20
(e.g., soil, sand,
seeweed)
40
60
80
100
51.4
10.2KT 58 F
FT
Rock
P. 52).
Assuming that its geological features are constant, the
Flat
displayed contour of a flat terrain has a uniform width.
The displayed contour of a hilly terrain has a long
1
tailing* . This is because the ultrasonic sent from the
transducer has a certain beam angle and hence
reflections from a bank vary in time of their returning to
Hilly
the transducer*
1
* The depth of water immediately underneath the ship
looks shallower than the actual depth.
2
* The displayed contour of a bank tends to be narrow.
48 21.417N 125 26.643W
0
20
40
60
80
100
43.4
10.2KT 58 F
FT
Assuming that its geological features are constant, the
displayed contour of a hard terrain has a uniform width.
The contour of a soft terrain is display loses redness in
color and has a short railing*
sand absorbs much of the ultrasonic.
1
* When slim constitutes the sea bottom, the low
frequency screen shows a long tailing.
Screen image
2
.
Screen image
1
. This is because soil or