Furuno FSV-84 manual Relation between bottom echo and tilt angle, Case 1 Tilt angle 30 to

2. HORIZONTAL MODE

2.4.3Relation between bottom echo and tilt angle

The figure at the top of the next page illustrates how two fish schools “a” and “b” are displayed on the screen using three different tilt angles.

Case 1: Tilt angle 30° to 40°

This tilt angle will display the entire bottom since it is captured by the full width of the beam. Fish school is obscured by the bottom.

Case 2: Tilt angle 10° to 20°

This tilt angle will only display half the bottom since it is captured by only the lower half of the beam. Fish school is located above the bottom.

Case 3: Tilt angle 0° to 5°

This tilt angle may or may not capture the bottom since the returning echo is weak. Fish school is located close to the bottom.

Case 1 Case 2 Case 3

		Fish school "a"
	Fish school "a"
Fish school "a"
		Fish sch	ool "b"
	Bottom	Bottom
Bottom
Case 1	Case 2	Case 3

Fish echo and tilt angle

Points to consider

•Normally, a vertically distributed fish school is a better sonar target than the bottom, because it reflects the transmitted pulse back toward the transducer.

•In case 3, both fish schools “a” and “b” are presented. Generally speaking, however, midwater fish schools tend to be larger than bottom fish schools and they are often displayed near the bottom on the display.

•It is difficult to detect bottom fish when they are not distributed vertically.

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