LORAN TD Setup
LORAN C is a radio navigation aid operated and maintained in the
United States by the United States Coast Guard. LORAN
(LOng RAnge Navigation) system covers the entire United States
and the U.S. Coastal Confluence Zone. From the perspective of a
mariner, the system is used for ocean and coastal navigation. It can
be used as a supplemental system for harbor and harbor approach
navigation, and it is used for inland navigation by recreational
vehicles.
LORAN TD Feature
The LORAN TD (Time Delay) feature eases the transition from
using LORAN to using GPS. The GPSMAP unit automatically
converts GPS coordinates to LORAN TDs for those who have a
collection of LORAN fixes for favorite fishing spots and other
waypoints recorded as TDs. You can show your location as a TD
or enter waypoints as TDs. The accuracy to be expected from this
conversion is approximately 30 meters. When the unit is placed
in the LORAN TD format mode, it simulates the operation of a
LORAN receiver. Position coordinates might be shown as TDs,
and all navigation functions can be used as if the unit was actually
receiving LORAN signals.
Using the LORAN TD Format
When creating new waypoints using LORAN TD coordinates, you
must set the correct LORAN chain number and secondary stations in
the
Setup TD
field before storing the waypoint. After the waypoint
is stored in the unit’s memory, it will always reference the LORAN
chain number and secondary stations currently selected in the
Setup TD
field. If you enter a different LORAN chain number or
change the secondary stations or offsets in the Setup TD field, the
active waypoint information will reflect those changes. Because
the GPSMAP 378/478 does not rely on the LORAN signal for
navigation, it can reference a different GRI chain and/or secondary
stations and still navigate to the location stored in memory.
The LORAN Location Format field is located on the Location sub
tab of the Setup tab on the Main Menu. The LORAN TD Setup
window contains the fields to select the Loran GRI-Chain Number,
Primary and Secondary Stations, and TD Offsets.
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GPSMAP 378/478 Owner’s Manual
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