Lowrance electronic LMS-520C - Manual (Page 78)

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A good way to gauge your speed sensor's performance is to compare its
reading with the ground speed measured by your unit's GPS functions.
When you make a run to compare GPS ground speed to speed sensor
speed, perform your test in relatively calm water free of current, if pos-
sible. (Unless, of course, you are taking the speed of current into con-
sideration when making your calculation.) After you have a correction
figure, here's how to enter it:
1. Press
MENU
|
MENU
| ↓ to
S
ONAR
S
ETUP
|
ENT
| ↓ to
C
ALIBRATE
W
ATER
S
PEED
|
ENT
.
2. Enter the number you calculated earlier: press ↑ or ↓ to change the
first character (+ or –), then press → to move the cursor to the next
number and repeat until the percentage is correct, then press
EXIT
.
Chart Speed
The rate that echoes scroll across the screen is called the chart speed.
The default is maximum; we recommend that you leave the speed set
there for virtually all fishing conditions.
You, however, might consider experimenting with chart speed when
you are stationary or drifting very slowly. You may sometimes achieve
better images as you slow down the chart speed to match how fast you
are moving across the bottom.
If you are at anchor, ice fishing or fishing from a dock, experiment with
a chart speed around 50 percent. If you are drifting slowly, try a chart
speed around 75 percent. When you are stationary and a fish swims
through the sonar signal cone, the image appears on the screen as a
long line instead of a fish arch. Reducing the chart speed may result in
a shorter line that more closely resembles a regular fish return.
Sonar Page menu with Chart Speed command selected (left).
Chart Speed Control Bar (right).