LORAN C Basics
LORAN C is a radio navigation aid operated and maintained in the United States
by the Untied 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. The LORAN C system is also used in civil aviation.
The LORAN system consists of groups of land based transmitter stations
called chains. A chain contains a master station (M) and at least two, but more
commonly 4 or 5 secondary stations designated (M) Victor, (W) Whiskey, (X)
Xray, (Y) Yankee, and (Z) Zulu. These stations are usually separated by hundreds
of miles. Each station transmits radio pulses at precise time intervals. The receiver
measures the difference in time it takes the pulsed signal from each
Master/Secondary pair to reach the receiver. This time is quite small, generally in
millionths of a second. These time differences are then displayed on the LORAN
receiver as the TD (time difference) coordinates.
Many of the transmitter stations serve multiple roles. A station can serve as a mas-
ter station for one chain and a secondary station for another, or as a secondary sta-
tion for multiple chains. An example would be the chain 9610 master station and
the chain 8970 Zulu station. These operate on the same transmitter located in
Boise City, Oklahoma. LORAN is being phased out as a primary source of naviga-
tion, but should remain active until after the turn of the century.
LORAN Chains located across the continental U.S.
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LORAN TDs
LORAN C Basics
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