Summer Vacation 2003 – ASF Spatial Mapping in CO, AR, FL, and CA 32 nd Annual Technical Symposium International Loran Association 5 Nov 2003 Boulder, CO

11/5/03USCGA-JJMA Presentation for ILA Authors  CAPT Richard Hartnett  US Coast Guard Academy  Gregory Johnson  John J. McMullen Assoc. Inc.  Dr. Peter Swaszek  University of Rhode Island  LT Todd Moyer  University of Rhode Island  Ruslan Shalaev  John J. McMullen Assoc. Inc.

11/5/03USCGA-JJMA Presentation for ILA Outline  Introduction and Goals  Experiment Description  Measurement system  BALOR model  ASF Gradients near airports  Model vs actual  Flights  Ground locations  Conclusions / Future Work

11/5/03USCGA-JJMA Presentation for ILA Introduction  LORAN-C as “the” backup for GPS  Accuracy, availability, integrity, continuity  Accuracy:  Needs:  Aviation: NPA – RNP 0.3 (309 meters)  Maritime: HEA (8-20 meters)  Limitations:  Spatial and temporal variations in TOA (ASF) observed by the receiver and presented to the position solution algorithm

11/5/03USCGA-JJMA Presentation for ILA Loran  Multi-station, multi-chain, all-in-view receiver  TOA vs. TD measurements  Separate “errors” into spatial, temporal, and directional components  DSP-based receivers  H-field vs. E-field antennas  Single ASF value for airport  As long as ASF gradient is within bounds

11/5/03USCGA-JJMA Presentation for ILA Current Research  USCGA/JJMA activities:  Explore ways to mitigate TOA variation  Current approach:  Model the ASF sources  Spatial effects  Temporal effects  Model the directional effects (H-field)  Estimate parameters/values for the models  “Correct” the TOA observations using the models Of interest today

11/5/03USCGA-JJMA Presentation for ILA ASF Variation Model  Assume that the variation in the observed TOAs can be decomposed into 3 independent, additive terms:  Spatial term:  Due to differences in the Loran signal propagation path  Temporal term:  For short term TOA variability on a local region  Directional term:  Based on the relative bearing of the Loran tower to the vessel Key assumptions

11/5/03USCGA-JJMA Presentation for ILA Experiment Description  Flight Data  Collect flight data to measure ASF variations in vicinity of airports  Fly approaches for later post-processing with ASFs  Ground Mobile Data  Collect ASF data at static locations around the airport out to 25 NM to assess ASF gradients and flight measurement performance  Ground Reference Station  Collect ASF data at fixed location during all other testing in order to factor out temporal ASF variations

11/5/03USCGA-JJMA Presentation for ILA Experiment Locations  4 States 10 Airports  Colorado  Grand Junction – Walker Field (GJT)  Montrose Regional (MTJ)  Rifle – Garfield County Regional (RIL)  Arkansas  Little Rock – Adams Field (LIT)  Hot Springs Memorial (HOT)  Florida  Pensacola Regional (PNS)  Panama City (PFN)  California  Monterey Peninsula (MRY)  Salinas Municipal (SNS)  Watsonville Municipal (WVI)

11/5/03USCGA-JJMA Presentation for ILA Flight tracks

11/5/03USCGA-JJMA Presentation for ILA Pictures of Locations Little Rock, ARGrand Junction, CO Pensacola, FLMonterey, CA

11/5/03USCGA-JJMA Presentation for ILA FAA Convair 580

11/5/03USCGA-JJMA Presentation for ILA ASF Mapping System (Flight) Aircraft H-field antenna Novatel OEM-4 WAAS GPS USCGA DDC Rcvr ICS Buffer swap signal DS-345 Signal Generator 10 MHz 25.6 MHz 2 Channels RF Save to disk: TIC, RAW TOA, ECD, SNR, GPS info, etc. Event time and GPS Data Heading Sensor Heading Frequency Devices 90IP

11/5/03USCGA-JJMA Presentation for ILA DDC and SatMate Rcvrs

11/5/03USCGA-JJMA Presentation for ILA ASF Mapping System (Mobile) H-field antenna BrandyWine Synchclock Board With Astech DG16 Receiver ICS 652 board ICS Buffer swap signal GPS-stabilized 25.6 MHz 2 Channels RF Save to disk: TIC, RAW TOA, ECD, SNR, GPS info, etc. Event time and GPS Data Heading Sensor Heading RF board CPU

11/5/03USCGA-JJMA Presentation for ILA Ground Mobile

11/5/03USCGA-JJMA Presentation for ILA Static ASF Measurement System (Monitor) E-field antenna LRS-IIID Rcvr NovAtel OEM4 GPS rcvr 10 MHz RF Gate Event time, GPS data Laptop running LocusNovAtel program Save to disk: ASFs, ECD, SNR, signal status, GPS info TOAs, ECD, SNR

11/5/03USCGA-JJMA Presentation for ILA Reference Station

11/5/03USCGA-JJMA Presentation for ILA Working round the clock!

11/5/03USCGA-JJMA Presentation for ILA Model  University of Wales, Bangor developed model – BALOR  Uses Monteath Method, integral solution  Terrain effects using DTED level 1  FCC Conductivity map  Coastline vectors

11/5/03USCGA-JJMA Presentation for ILA BALOR  Fixed Locations  BALOR used to calculate predicted ASF values for selected locations  Same locations where JJMA team collected ASF data  Modeled using small 4-point grids  by degree area  Airborne ASF data  BALOR used to calculate a grid over flight area  grid resolution set to 0.01 degree

11/5/03USCGA-JJMA Presentation for ILA © Paul Williams, University of Wales, Bangor

11/5/03USCGA-JJMA Presentation for ILA TOA ASFs  Define TOA ASF as the additional propagation delay due to a non-seawater path  due to terrain and conductivity differences  Difference between measured and predicted (PFSF) TOA is ASF + time offsets

11/5/03USCGA-JJMA Presentation for ILA Relative ASFs  Use fixed reference station to eliminate system timing errors from the ASF value  So the measured values are actually relative ASFs – relative to the fixed monitoring site  Although not TRUE ASFs, still valid for assessing gradients in airport area  To compare to model must apply a fixed correction to all ASF values so that model and measurements are relative to same value

11/5/03USCGA-JJMA Presentation for ILA BALOR Model for Montrose

11/5/03USCGA-JJMA Presentation for ILA BALOR Model for Montrose

11/5/03USCGA-JJMA Presentation for ILA Montrose 0 and 9700ft elev

11/5/03USCGA-JJMA Presentation for ILA Measured Data Locations

11/5/03USCGA-JJMA Presentation for ILA

11/5/03USCGA-JJMA Presentation for ILA Fixed Locations vs Model

11/5/03USCGA-JJMA Presentation for ILA Fixed Locations vs Model

11/5/03USCGA-JJMA Presentation for ILA Fixed Locations vs Model

11/5/03USCGA-JJMA Presentation for ILA Point Piños Area

11/5/03USCGA-JJMA Presentation for ILA Flights vs Model Grid

11/5/03USCGA-JJMA Presentation for ILA Flights vs Model Grid

11/5/03USCGA-JJMA Presentation for ILA Flights vs Model Grid

11/5/03USCGA-JJMA Presentation for ILA Flights vs Model Grid

11/5/03USCGA-JJMA Presentation for ILA Conclusions / Future Work  Model appears to perform reasonably well; needs some tweaking however  Comparison to ground level points pretty good  Altitude performance….  Still need to assess bias in model  Model can be used to assess gradients in the vicinity of an airport  Continue to analyze data to assess position performance using single set of ASF values for each airport

11/5/03USCGA-JJMA Presentation for ILA Acknowledgements  Mitch Narins, FAA AND  FAA Technical Center  JJMA Team  Christian Oates  George Sanders  Tim Waldie  Ken Dykstra

Questions?