Canadian Coast Guard World Wide Web

Canadian Coast Guard

Marine Communications & Traffic Services

RAMN 2005

U.S. WEST COAST LORAN-C CHAIN, GRI 9940

STATION

LATITUDE

LONGITUDE (2)

FUNCTION

EMISSION

DELAY

THEORETICAL

BASELINE

TRAVEL TIME (3)

RADIATED

PEAK

POWER

FALLON,

Nevada (1)

39 33 06.74N

118 49 55.82W

MASTER

—

400 kW

GEORGE,

Washington (1)

47 03 48.10N

119 44 38.98W

W SECONDARY

13796.90 m s

2796.90 m s

1400 kW

MIDDLETON,

California (1)

38 46 57.11N

112 29 43.98W

X SECONDARY

28094.50 m s

1094.50 m s

400 kW

SEARCHLIGHT,

Nevada (1)

35 19 18.31N

114 48 16.88W

Y SECONDARY

41967.30 m s

1967.30 m s

560 kW

This station operated by United States of America.

Based on WGS 84 Datum (Coordinate system for charting).

Theoretical Baseline Travel Time is based on all-seawater transmission path between master and secondary

TABLE 4

NORTH CENTRAL U.S. LORAN-C CHAIN GRI 8290

STATION

LATITUDE

LONGITUDE (2)

FUNCTION

EMISSION

DELAY

THEORETICAL

BASELINE

TRAVEL TIME (3)

RADIATED

PEAK

POWER

HAVRE,

Montana (1)

48 44 38.59N

109 58 53.613W

MASTER

—

400 kW

BAUDETTE,

Minnesota (1)

48 36 49.95N

94 33 17.92W

W SECONDARY

14786.56 m s

3786.56 m s

800 kW

GILLETTE,

Wyoming (1)

44 00 11.1N

105 37 23.90W

X SECONDARY

29084.44 m s

2084.44 m s

400 kW

WILLIAMS LAKE ,

B.C.

51 57 58.88N

122 22 01.69W

Y SECONDARY

45171.62 m s

3171.62 m s

400 kW

This station operated by the United States of America.

Based on WGS 84 (coordinate system for charting).

Theoretical Baseline Travel Time is based on all-seawater transmission path between master and secondary.

Loran-C Coordinate Converters

Many of the Loran-C Coordinate Converters on the market do not compensate for the overland propagation errors caused by radio waves travelling more slowly over land than they do over seawater. These converters assume that the radio waves are travelling over an all seawater path from the transmitters to the ship. Because the amount of the time delay in each pattern varies with location, as does the width for 1 microsecond in each pattern, and the angle of cut between patterns, and which two patterns are being used for the position determination, there can be no over-all simple error statement.

It is important to note that a Loran-C coordinate converter that does not incorporate the overland propagation corrections (Additional Secondary Factor, or ASF) within its computations will produce a systematic geographic position error. This error is often in the dangerous direction; namely, it will compute a position that is farther offshore. If you are transiting along a coast, thinking that you are safely outside the dangerous shoals, you may find yourself closer to shore than you think you are.

The Canadian Hydrographic Service (CHS) has determined the overland propagation (ASF) errors through actual observations. The overland propagation corrections were incorporated into the lattices that were/are on CHS nautical charts. These maps have been published maps showing the corrections to observed Time Differences (TD’s) necessary to make them theoretical TD’s that can be used with algorithms using just the seawater velocity to compute the geographic position.

Manufacturers have their own methods to compute geographic positions, which may incorporate some approximations. The receivers may or may not tell the mariner which TD’s it is using to compute the position – hopefully the pair with the best repeatable geometry. Some receivers use more than two TD’s to compute positions.

Some manufacturers have incorporated the overland propagation corrections into their algorithms and those receivers should perform more accurately than those that do not. The industry self-imposed standard set by the Radio Technical Commission on Marine Services – Special Committee 75 on Minimum Performance Standards for Loran-C Coordinate Converters (1980) is a ¼ mile positioning accuracy.

The following tables give the vectors from the Loran-C coordinate converter position to the true position. These will give some guide as to the possible errors. It is suggested, however, that mariners NOT correct their positions by the stated amounts, but to use the listed information as an advisory. Your coordinate converter may behave differently.

5990 – Canadian West Coast Chain

Information in Bold is for the TD pair that gives the best repeatability.

Vicinity of:	Latitude	Longitude	5990XY	5990XZ	5990YZ

Gulf of Georgia
Cape Mudge	49 55N	125 10W			0.0 nm
Cape Lazo	49 45N	124 45W			0.0 nm
Sisters Islets	49 30N	124 30W			0.0 nm
Nanaimo	49 15N	123 55W			0.1 nm @ 055°T
Point Grey	49 15N	123 20W			0.1 nm @ 080°T
Patos Island	48 45N	123 00W			0.1 nm @ 095°T

Juan de Fuca Strait
Hein Bank	48 20N	123 00W			0.2 nm @ 225°T
Trial Island	48 20N	123 20W			0.2 nm @ 235°T
Race Rocks	48 15N	123 30W			0.1 nm @ 230°T
Port Renfrew	48 30N	124 30W			0.2 nm @ 015°T
Neah Bay, Wash	48 23N	124 35W			0.1 nm @ 035°T

Vancouver Island, West Coast
Amphitrite Point	48 50N	125 30W	0.1 nm @ 345°T		0.1 nm @ 045°T
Estevan Point	49 15N	126 30W	0.1 nm @ 090°T		0.1 nm @ 085°T
Cape Cook	50 00N	128 00W	0.3 nm @ 155°T	0.7 nm @ 185°T	0.5 nm @ 115°T
Triangle Island	51 00N	129 00W	0.6 nm @ 190°T	0.4 nm @ 060°T

Queen Charlotte Sound
Pine Island	51 00N	127 45W	0.2 nm @ 175°T	0.3 nm @ 040°T
Goose Group	52 00N	129 00W	0.4 nm @ 195°T	0.4 nm @ 055°T
E of Kunghit I	52 00N	130 30W	0.4 nm @ 175°T	0.5 nm @ 080°T

5990 – Canadian West Coast Chain

Information in Bold is for the TD pair that gives the best repeatability.

Vicinity of:	Latitude	Longitude	5990XY	5990XZ	5990YZ

Hecate Strait
Hecate Strait	53 00N	131 00W	0.5 nm @ 195°T	0.7 nm @ 075°T
Seal Rocks	54 00N	131 00W	0.6 nm @ 190°T	0.9 nm @ 080°T

Dixon Entrance
Chatham Sound	54 30N	130 35W		0.6 nm @ 075°T
Zayas Island	54 35N	131 10W		0.8 nm @ 085°T
Cape Chacun	54 40N	132 00W	0.4 nm @ 120°T	1.1 nm @ 085°T
Masset	54 10N	132 00W	0.7 nm @ 215°T	1.1 nm @ 080°T
Forrester Island	54 40N	133 30W	0.6 nm @ 145°T	1.2 nm @ 100°T

Queen Charlotte Islands, West Coast
Langara Island	54 20N	133 15W	0.7 nm @ 215°T	1.3 nm @ 095°T
Buck Point	53 10N	133 00W	0.6 nm @ 200°T	0.7 nm @ 090°T
W of Kunghit I	52 00N	131 30W	0.4 nm @ 180°T	0.6 nm @ 075°T

Offshore, near the 200 nm limit
	46 30N	129 00W	0.7 nm @ 065°T	0.7 nm @ 060°T	0.7 nm @ 065°T
	49 00N	133 00W	0.4 nm @ 130°T
	51 30N	137 00W	0.5 nm @ 160°T	1.8 nm @ 075°T
	54 00N	137 00W		2.1 nm @ 095°T

Updated: 18/07/2005

Important Notices