Anchor Mode - Raymarine LIGHTHOUSE 4 Operation Instructions Manual

14.1 Anchor mode

Anchor mode should be used when your vessel is at anchor. Anchor mode
uses your vessel's GNSS (GPS) position to record your location when your
anchor hits the bottom. Anchor mode will calculate if your vessel has
dragged its anchor from its original location, based on specified values and
then trigger the Anchor drag alarm. To activate the anchor drag alarm the
Anchoring wizard must be completed.
Note:
[Anchor mode] does not take into account effects that tide may have on
chain length or depth values.
Before Anchor mode can be used the system requires the following details:
• GNSS (GPS) position — via a connected receiver.
• Depth — via a connected transducer.
• Length of your vessel (bow to stern)— value specified in [Boat length] field.
• GNSS (GPS) receiver distance from vessel's bow — value specified in [Bow
to GPS] field.
[Boat length] and [Bow to GPS] can be set in the [Boat details] settings tab:
[Homescreen > Settings > Boat details]. If the values have not been set then
you will be prompted to enter them when activating [Anchor mode] for the
first time.
Note:
If depth data and position data are not available you will not be able to
start the anchoring wizard.
Anchor mode uses the following data, measurements and calculations:
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1. Maximum swing radius — calculation determined using Boat length,
Bow to GPS distance, Chain length and Depth.
2. Drag limit — calculation determined using Maximum swing radius, Boat
length and Bow to GPS distance.
3. Boat length — user defined measurement.
4. Bow to GPS — user defined measurement.
5. Waterline to deck — 1 meter is add to the calculation to allow for the
distance from the waterline to the deck.
6. Depth — data received from depth transducer.
7. Depth offset — the specified depth offset is added to the calculation.
The depth offset is based on your transducer settings (Zero if [Below
transducer] is selected, positive value if [Below waterline] is selected and
negative value if [Below keel] is selected.) Refer to:
8. Chain length — default calculation based on 4 times depth. Chain length
can be altered manually to specify actual chain length.
The anchor drag alarm is triggered if your GNSS (GPS) receiver passes the
distance from the original anchor position by the specified drag limit distance.
When anchor mode is active a track of your vessels movements will be
recorded and representative graphics will be displayed onscreen in the chart
app.
p.262 — Depth offset