LORAN-C in ParadiseLORAN-C in Paradise

International Loran Association

31st Annual Convention and Technical Symposium

October 27-30, 2002

Washington, DC

Written and Presented by:

John B. Moore, Jr., Principal EngineerW R Systems, Ltd. (member ILA)2500 Almeda Avenue, Suite 214Norfolk, VA 23513-2403jmoore@wrsystems.comTelephone: (757) 858-6000, ext. 430

OutlineOutline

Acquisition time S/R ratio

Introduction

W R Systems Navigation Overview

Objectives of Paper

Observations of LORAN-C Performance

(Continued on next slide)

Own ship tracking Accuracy vs. GPS (WAAS) Ease of use Observation of data

Conclusion

Outline - (continued)Outline - (continued)

Navigation OverviewNavigation Overview Provide NAVCERT testing of U.S. Navy

ship navigation systems

INS, GPS, Nav inputs to landing systems, weapons

Previously evaluated LORAN-C when it was installed

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WRSystems supporting the development of ECDIS-N charting

No LORAN-C currently installed

Totally GPS dependent

Navigation Overview - (continued)Navigation Overview - (continued)

Objectives of Paper Objectives of Paper Look at accuracy of LORAN-C compared

to GPS (WAAS)

Make observations of LORAN-C usability for navigation, acquisition, SNR, ease of use, etc.

Try to support value of LORAN-C showing useful data

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Objectives of Paper - (continued)Objectives of Paper - (continued)

Recent experience with LORAN-C (not much data around it seems)

Unfunded, personnel effort to satisfy my curiosity

S/Y L’AMOURS/Y L’AMOUR

Observations Observations Acquisition Time

10-20 minutes. Seemed to be dependent on where you were in net. Note that LORAN-C would not lock on on one occasion in the Bahamas. While no acquisition data was taken, acquisition time seemed longer on the outer edge of the net in the Bahamas.

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Observations - (continued)Observations - (continued)

Own ship tracking of SMG, HMG, XTE, etc. correlated with GPS. At sailboat speed (5-7 knots), tracking good.

S/R ratios were observed to be 80s and 90s throughout, although data not recorded. Signal strength always seemed to be good.

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Observations - (continued)Observations - (continued)

Accuracy GPS (WAAS) – LORAN-C All comparisons in position (L) taken

at anchor or dockside. (GPS (WAAS) verified on charts)

Ease of use

LORAN-C receiver equally functional and easy to use. Larger size actually easier to operate.

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Observations - (continued)Observations - (continued) Observation of difference data

All coastal [GPS (WAAS)] – [LORAN-C] comparisons were within 0.25 nm, as published in the LORAN-C Users Handbook with one exception

Exception: In Ft. Lauderdale, QRM level very high. Cycle slip believed to cause errors of 0.5 nm. It must be noted that the high QRM did not affect GPS. Unable to operate HF ham radio most of the time.

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Observations - (continued)Observations - (continued)

Errors in outer reaches of LORAN-C net 0.8 nm to 1.5 nm. While these errors are much higher than GPS (WAAS), it is adequate for ocean navigating.

Note difference of 1.475 at west end, and errors of .882 and .971 at Great Sale Cay and Allen Pensacola Cays, Bahamas. These cays are further east.

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Observations - (continued)Observations - (continued)

Note reading at Allen Pensacola Cay readings on 3/19/02 and 4/17/02 with a difference of .049 nm 100 m repeatability. Note Great Guana repeatability of 70 m. Marathon 150 m. Looks like repeatability is 150 m or better.

Not sure that I took enough data at each location, over enough time to draw any final conclusions, but we can see where further study would be needed.

GPS (WAAS) VS. LORAN-C

L λ L λ ΔL Δλ2/20/02; 0845 Marathon, FL 2442.724 08104.914 2442.65 08104.95 0.07 -0.04 0.0822/21/02; 0815 Marathon, FL 2442.725 08104.914 2442.57 08104.95 0.15 -0.04 0.1592/25/02; 0825 Marathon, FL 2442.723 08104.912 2442.58 08104.98 0.14 -0.07 0.1583/2/02; 0920 Marathon, FL 2442.724 08104.913 2442.6 08104.95 0.12 -0.04 0.1293/16/02; 0850 West End, Bahamas 2642.096 07859.48 2640.89 07858.63 1.206 0.85 1.4753/17/02; 1745 Gr. Sale, Bahamas 2658.663 07813.083 2658.06 07812.44 0.60 0.64 0.8823/19/2002 Allen Pensacola, Bahmas 2659.36 07741.37 2658.72 07740.64 0.64 0.73 0.9713/21/2002 Green Turtle, Bahamas 2645.617 07719.494 2644.76 07718.58 0.86 0.91 1.2533/24/2002 Munjack Cay, Bahamas 2649.101 07721.896 2648.23 07721.13 0.87 0.77 1.160

3/26/2002 Bakers Bay, Bahamas 2641.342 07709.456WOULD NOT

LOCK ONWOULD NOT

LOCK ON -- -- --Bakers Bay, Bahamas 2641.327 07709.449 2640.44 07708.48 0.89 0.97 1.314

3/28/2002 Gr. Guana, Bahamas 2641.326 07709.451 2640.34 07708.56 0.99 0.89 1.3293/29/2002 Gr. Guana Harbor, Bahamas 2639.793 07706.653 2638.93 07705.71 0.86 0.94 1.2783/31/2002 Gr. Guana Harbor, Bahamas 2639.792 07706.651 2638.92 07705.67 0.87 0.98 1.3134/5/2002 Hope Town, Bahamas 2632.241 07657.569 2631.22 07656.53 1.02 1.04 1.4574/7/2002 Hope Town, Bahamas 2632.162 07657.724 2631.15 07656.69 1.01 1.03 1.4474/9/2002 Marsh Harbor, Bahamas 2633.052 07703.289 2632.05 07702.25 1.00 1.04 1.4434/17/2002 Allen Pensacola, Bahamas 2659.345 07741.358 2658.62 07740.64 0.72 0.72 1.0204/21/2002 Ft. Lauderdale, FL 2607.435 08007.207 2607.06 08006.95 0.38 0.26 0.4554/29/2002 Ft. Lauderdale, FL 2607.439 08007.203 2606.98 08006.92 0.46 0.28 0.5395/7/2002 Ft. Lauderdale, FL 2607.43 08007.207 2607.05 08006.96 0.38 0.25 0.4535/8/2002 Ft. Lauderdale, FL 2607.439 08007.204 2607.00 08006.94 0.44 0.26 0.5125/12/2002 Titusville, FL 28037.396 08048.270 28037.44 008048.10 -0.04 0.17 0.1765/14/2002 Daytona, FL 2912.255 08100.845 2912.29 08100.68 -0.03 0.16 0.1695/20/2002 Thunderbolt, GA 3201.473 08102.863 3201.42 08102.81 0.05 0.05 0.0755/23/2002 Charleston, SC 3246.774 07957.318 3246.68 07957.23 0.09 0.09 0.1295/24/2002 Georgetwon, SC 3321.879 07916.987 3321.76 07916.88 0.12 0.11 0.1605/26/2002 Wrightsville Beach, NC 3412.421 07747.988 3412.27 07747.78 0.15 0.21 0.2575/27/2002 Swansboro, NC 3440.805 07706.733 3440.67 07706.62 0.13 0.11 0.1765/29/2007 Beauford, NC (N of) 3448.344 07641.115 3448.23 07641.03 0.11 0.09 0.1425/31/2002 Dowry Creek, Bellhaven, NC 3532.016 07632.116 3531.91 07632.02 0.11 0.10 0.143

DATE/TIME LOCATION CEP

GPS (WAAS) GPS –L

ConclusionsConclusions

LORAN-C performance using 1980 technology versus GPS (WAAS) using 2000 technology seemed good

LORAN-C is a good backup to GPS for coastal navigation at least

(Continued on next slide)

LORAN-C has all the navigation features (functions) of GPS except vertical position

Meets 0.25 accuracy

Conclusions - (continued)Conclusions - (continued)

Repeatability better than 150 meters

(Continued on next slide)

LORAN-C updated receiver design should improve: accuracy

Conclusions - (continued)Conclusions - (continued)

receiver size/weight GPS/LORAN-C Kalman filter improves GPS/WAAS-C accuracy

(Continued on next slide)

Public acceptance of LORAN-C for navigation dependent on:

accuracy improvement

Conclusions - (continued)Conclusions - (continued)

receiver and system performance

size/weight/deduction

(Continued on next slide)

low cost

Accuracy improvements achievable through:

faster processors

Conclusions - (continued)Conclusions - (continued)

additional error correction (i.e., secondary phase correction)

(Continued on next slide)

Conclusions - (continued)Conclusions - (continued)

improved algorithms to utilize master and slave independent solutions

rho – rho solutions

LORAN-C is a very user “friendly” system