Furuno CSH-5L/CSH-8L Bottom and tilt angle, How to discriminate fish echoes from the bottom, 1-12

1. OPERATIONAL OVERVIEW

1.4.2Bottom and tilt angle

Finding the proper tilt angle is of utmost importance when searching for fish, especially in coastal water fishing, where the depth of the fishing ground is from 50-100 m. In this type of fishing ground it is imperative that the bottom echo be always displayed to properly distinguish between fish and the bottom. When selecting a tilt angle, keep the following points in mind.

Case 1: Tilt angle 30 to 40 degrees

This tilt angle uses the full beamwidth to receive echoes, thus the entire bottom echo is displayed. Fish echoes may be hidden in the bottom echo.

Case 2: Tilt angle 10 to 20 degrees

This tilt angle receives bottom echoes within the bottom half of the beam. Fish echoes astern of the bottom echo are displayed.

Case 3: Tilt angle 0 to 5 degrees

This tilt angle may or may not display returning echoes. Fish echoes near the bottom echo are displayed.

1.4.3How to discriminate fish echoes from the bottom

The following figure illustrates how two fish schools (a) and (b) are displayed on screen using three different tilt angles.

Case 1: Tilt angle 30 to 40 degrees

Fish school is obscured by the bottom echo.

Case 2: Tilt angle 10 to 20 degrees

Fish school is located above the bottom echo (midwater).

Case 3: Tilt angle 0 to 5 degrees

Fish school is located close to the bottom echo.

Case 1			Case 2		Case 3
					b
			a	a	a
Fish s	ch	ool (a)		Fish school (a)	Fish school (a)
					Bottom
Bottom				Bottom	(b)

Case 1 Case 2 Case 3

How to discriminate fish echoes from bottom

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