Humminbird manual USING THE 405SX, What You See On-Screen

Surface Clutter Rocky Bottom

USING THE 405SX

WHAT YOU SEE ON-SCREEN

This range is selected so the bottom representation is typically shown about ²⁄₃ down the display.

Bottom. The graphic depiction of the bottom provides the user with an effective tool for understanding the composition of the bottom. The FSTN type display uses 4 discrete levels of gray to indicate the intensity of the returned sonar signal. The 405SX can display even the smallest sonar returns with light gray pixels. Larger returns are displayed with darker shades of gray. If the bottom is hard and smooth, the bottom depiction is narrow and dense. If the bottom is soft mud or sand, the depiction will be thick and less dense. This indicates that much of the signal is absorbed by the soft bottom. If the bottom is rocky or rugged in composition, the depiction is of varying density and textured in appearance.

Wave action also affects the bottom depiction. The information drawn is a distance measurement, so if the boat is moving up and down over flat bottom, the bottom depiction often appears in regular variations that match wave timing.

Structure. Structure is defined as any object physically attached to the bottom. The sonar configuration of the 405SX is optimized to give the most accurate depiction of bottom structure possible. Grass, trees, stumps, wrecks or other debris are accurately displayed, however the depiction of these objects varies with boat speed and direction. The

best way to learn to interpret structure is to operate the 405SX

over a variety of known conditions and experiment with user functions

to best represent those conditions on-screen.

Surface Clutter. Surface clutter is the layer of water near the surface that is rich in algae and other growth, and often is aerated by wind or wave action. This area of

water interferes with	sonar
transmission and often appears on-
screen as regular clusters of ind-
ividual dots near the “0” line.		Hard Bottom Soft Bottom

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