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Predicting Differential Loran-C Performance in Boston Harbor

Predicting Differential Loran-C Performance in Boston Harbor. Erik Johannessen Andre Grebnev Wouter Pelgrum . Context. Supports on-going LORIPP/LORAPP evaluations and analyses Specifically part of a program to prototype Integrated GPS/Loran for Harbor Entrance and Approach

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Predicting Differential Loran-C Performance in Boston Harbor

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  1. Predicting Differential Loran-C Performance in Boston Harbor Erik JohannessenAndre Grebnev Wouter Pelgrum

  2. Context • Supports on-going LORIPP/LORAPP evaluations and analyses • Specifically part of a program to prototype Integrated GPS/Loran for Harbor Entrance and Approach • Program Participants

  3. HEA Receiver Program Scope • Prototype Integrated Receivers • Receiver/Integration Specification • Antenna Design • Cost Study • 5 Deliverable Evaluation Units • Measurement Campaign • On-the-Water Data Collection • Reference Station Measurements • Demonstration • Documentation

  4. Prototype Integrated Receivers • Reelektronika develops miniature integrated GPS/Loran-C receiver as OEM product for NELS (Northwest European Loran System) Signal Processor77 x 51 mm Front End & ADC77 x 47 mm Credit Card 85 x 54 mm

  5. Prototype Integrated Receivers (cont’d) Replace MF Beacon Engine with Loran/GPS/WAAS Modify H-Field Beacon Antenna To H-Field Loran

  6. Measurement Campaign Overview • Envisioned as three steps leading to set up capable of formal demo in DC area • First step local to Megapulse resource availability • Temporal and spatial decorrelation measured, also local effects • Differential measurements by tightly time coupling a reference and rover • Method applicable to all modes • Stored raw sample data permits comparison of multiple envelope and carrier tracking points

  7. Experimental Set-up – Step 1 Reference Station at Megapulse Rover Receiving Equipment Suite

  8. A lovely day for a sail?

  9. Reference Station Data Measurement Date : June 20, 2003 1100-1800 ET Recorded at Megapulse –(Nan, Sen, Crb, CB shown) 5 sec independent samples Non-moving average of 12 samples

  10. Reference Station Data (cont’d) • Note: discrete steps of 20 ns - LPAs or Other?? Nantucket – last 3.5 hours Caribou – 7 hours, 10nsec/div

  11. Reference Station Data (cont’d) • Scatter plot created using 7 TOAs, 5 sec integrated/independent • Repeatability of 7 hour set: 6.5m, 95% and 8.6m, 99% • Slight offset from mean due to ASF variation

  12. Reference Station Data (cont’d) • Mean of 1st minute used to compensate next twelve 5 sec samples • Repeatability improves slightly: 6.1m, 95% and 8.2m, 99%

  13. Reference Station Data (cont’d) • Mean of ten minutes used to compensate next 120 samples • Repeatability: 6.2m, 95% and 8.4m, 99%

  14. Rover Receiver Results/Issues • Antenna related • Phase error with orientation • Include cable and attenuators as part of antenna • Receiver related • Data grabber worked very well • Need to lose some weight • Vessel related • Alternator noise

  15. Measurements-Step 2 • Currently completing analysis of Step 1 Rover Results • Antenna related issues addressed via hardware upgrade and compensation in software • Ship Shape gone to FLA for winter, will need alternate vessel • Alternatively, SiTex resources in Tampa • Expect to be on water again early December

  16. Summary • Reference station and Rover data collection systems useful for post processing • High update rate of differential correction did not significantly improve position fix • Vessel related issues need resolution • Measurement campaign has been critical input to integrated receiver design

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