Thermocline
Slope
Second Return
Sloped Bottoms
Bottoms having a large degree of slope also present a unique picture. These generally have a thicker black band representing the bottom directly under the boat. Equal areas of gray above and below the black band represent sonar returns from around the boat.
Second Sonar Returns
A second sonar return may be visible if the appropriate depth range is selected. This appears as a depth contour below the main bottom contour, at twice the depth. The second return occurs when the sonar signal bounces between the bottom and the surface of the water, then back again. Some anglers use the appearance of the second return to determine bottom hardness. With a lower gain setting the second return will be more faint, except in areas with a hard bottom. The LEGEND 2000 SERIES has a unique depth range feature which permits the second return to be visible in any depth range up to
Structure
The LEGEND 2000 SERIES displays structure, such as submerged grass, brush, trees and wrecks on the bottom. Structure can be distinguished by comparing the area just above and below the main bottom return. Usually structure shows as areas of dark to light gray on top of a dark bottom contour. The appearance of structure is greatly affected by boat speed and direction; to repeat the same image it is often necessary to travel the same speed and direction over the location where the structure was originally located.
Thermoclines
The LEGEND 2000 SERIES is also capable of showing layers of water having different temperatures. These temperature differences, called thermoclines, appear at different depths, depending on current conditions.
USING THE LEGEND 2000 SERIES
CHART WINDOW / BOTTOMS / FISH APPEARANCE
A thermocline typically appears as a continuous band of many gray levels moving across the display at the same depth. Thermoclines always appear above the bottom.
Bait fish
Fish Arch
Partial Fish
Arch
Structure
Fish Appearance
Schools of bait fish as well as individual fish are clearly visible on the LEGEND 2000 SERIES display. Bait fish appear as “clouds” having different shapes and sizes depending on the number of fish and boat speed. Individual fish appear as smaller black and gray lines, often appearing as a “fish arch”. A fish arch may form as the fish moves through the sonar beam. Due to the transducer beam angle, the distance to the fish decreases as the fish moves into the beam, and then increases as it moves out again. When the CHART WINDOW graphs this distance change, an arch appears. Boat speed, the CHART SPEED setting and movement of the fish greatly affect the shape of the arch. When the boat and the fish are moving slowly relative to each other, the fish creates an elongated arch. When the boat and the fish are moving quickly relative to each other, the fish creates a shorter arch. A partial arch forms when the fish does not move through the entire cone angle.
Note: It is important to remember that sonar cannot distinguish between a fish and some other object suspended in the water. Regardless of the object the sonar detects, it has the possibility of being drawn as an arch.
Fish Arch Diagram
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