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68 GPSMAP 76 Owner’s Manual
APPENDIX > LORAN TD
Loran TD System
LORAN C is a radio navigation aid operated and
maintained in the United States by the United States
Coast Guard. The name LORAN is an acronym for
“LOng RAnge Navigation.” The LORAN 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 display your
position as a TD or enter waypoints as TDs. The
accuracy to be expected from this conversion is
approximately thirty meters. When the unit is placed
in the LORAN TD format mode, it simulates the
operation of a LORAN receiver. Position coordinates
may be displayed as TDs, and all navigation functions
may 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 unit memory, it will always reference
the LORAN chain number and secondary stations