Eagle IntelliMap 642C iGPS, Installation And Operation Instructions Manual

Page: 78 / 196

70
Set Keel Offset
This unit measures water depth from the face of the transducer. Since
the transducer is installed below the water surface, the distance dis-
played by the digital depth, chart depth scale, chart cursor or fish sym-
bols is
not the exact water depth. If the transducer is 1 foot below the
surface, and the screen shows the water depth as 30 feet, then the ac-
tual depth is 31 feet.
On sailboats or other large vessels with deep drafts, the distance be-
tween the transducer installation and the keel or lower engine unit can
be several feet. In those cases, an inexact depth reading could result in
grounding or striking underwater structure. The Keel Offset feature
eliminates the need for the navigator to mentally calculate how much
water is under his keel.
Keel Offset lets you calibrate the digital depth, chart depth scale, chart
cursor depth and fish symbol depth displayed on the screen. To calibrate
the depth indicators, first measure the distance from the face of the
transducer to the lowest part of the boat. In this example, we will use 3.5
feet. This will entered as a
negative 3.5 feet, which makes the depth indi-
cators perform as if the transducer's lower in the water than it really is.
1. Press
MENU
|
MENU
|
↓
to
S
ONAR
S
ETUP
|
ENT
|
↓
to
S
ET
K
EEL
O
FFSET
|
ENT
.
2. The Keel Offset dialog box appears. Press
↓
to change the plus (+)
sign to a minus (–) sign.
3. Press
→
to the first number, then press
↑
to change the number to 3.
4. Press
→
to the second number, then press
↑
to change the number to
5 and press
EXIT
. The depth indicators now accurately show the depth
of water beneath the keel.
NOTE:
If knowing the exact depth of water beneath the keel is less important,
you can calibrate the depth indicators so that they show the actual wa-
ter depth from surface to bottom. To do this, measure the distance
from the face of the transducer up to the surface (the water line on the
boat). In this example, we will use 1.5 feet. This will be entered as a
positive 1.5 feet, which makes the depth indicators perform as if the
transducer's higher in the water than it really is.
1. Press
MENU
|
MENU
|
↓
to
S
ONAR
S
ETUP
|
ENT
|
↓
to
S
ET
K
EEL
O
FF-
SET
|
ENT
.
2. The Keel Offset dialog box appears with a plus (+) sign at the
front of the box.