LORAN-C in Paradise International Loran Association 31 st Annual Convention and Technical Symposium October 27-30, 2002 Washington, DC Written and Presented by: John B. Moore, Jr., Principal Engineer W R Systems, Ltd. (member ILA) 2500 Almeda Avenue, Suite 214 Norfolk, VA Telephone: (757) , ext. 430

Outline  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)

Navigation 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 (Continued on next slide)

 WRSystems supporting the development of ECDIS-N charting  No LORAN-C currently installed  Totally GPS dependent Navigation Overview - (continued)

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 (Continued on next slide)

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’AMOUR

Observations  Acquisition Time  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. (Continued on next slide)

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. (Continued on next slide)

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. (Continued on next slide)

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. (Continued on next slide)

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 at west end, and errors of.882 and.971 at Great Sale Cay and Allen Pensacola Cays, Bahamas. These cays are further east. (Continued on next slide)

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

Conclusions  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)  Repeatability better than 150 meters (Continued on next slide)

 LORAN-C updated receiver design should improve:  accuracy 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)  receiver and system performance  size/weight/deduction (Continued on next slide)  low cost

 Accuracy improvements achievable through:  faster processors Conclusions - (continued)  additional error correction (i.e., secondary phase correction) (Continued on next slide)

Conclusions - (continued)  improved algorithms to utilize master and slave independent solutions  rho – rho solutions  LORAN-C is a very user “friendly” system