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88 GPSMAP 176/176C 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 always references 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 reflects those changes. Since the GPSMAP
176/176C 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.