About Bottom Slopes - Simrad ES70 - REFERENCE MANUAL REV A Reference Manual

Related topics
• How to adjust the pulse duration on page 82
• Normal Operation on page 121

About bottom slopes

"Bottom slopes" is a well known phenomenon with echo sounders.
On the echo sounder the phenomenon will appear by causing the bottom line (E) to be
distorted. All the echoes above the white line here are really a part of the bottom.
To minimize this phenomenon on the ES70 you can open the
right-clicking the depth presentation, and then change the setting for
. By increasing the number (more negative!) the bottom detector will become more
Level
sensitive, and the bottom will be detected earlier. On the echogram the white line will
"climb" up the slope. Make sure that you do not increase the sensitivity too much, as this
will have an effect on the fish detection on a flat bottom. Our experience show that a
sensitivity of approximately -75 dB can be used safely.
An other method for minimizing this phenomenon is to use a transducer with narrow
beam, or to increase the pulse duration.
338106/A
The edge of the beam (A) hits the bottom
first, and starts to give an echo. The bottom
detector in the echo sounder measures the
strongest echo, detects what it thinks is the
bottom, and starts the white line (C). The
area above the bottom detection (B) will be
masked off, and even though it may contain
fish these will not be visible because the
echo from the bottom is stronger than those
from the fish. The estimated depth (C) will
be shown.
Bottom Detector
Echo sounder theory
dialog by
Backstep Minimum
209