High Accuracy-Nationwide Differential Global Positioning System Test and Analysis: Phase II Report
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Table of Contents
The Nationwide Differential Global Positioning System (NDGPS) Modernization
Program is a multiagency effort to examine the viability of long baseline
carrier phase differential correction techniques. Phase I of this program
analyzed the broadcast of GPS observables from a single NDGPS site, Hagerstown,
MD, to aid in determining the appropriate signal structure and compression
techniques to support long range carrier phase operations. In Phase II a
second facility near Hawk Run, PA, was installed, enabling multiple baseline
carrier and code phase navigation solutions.
This first report verifies the original accuracy achieved (10 cm, 95 percent
horizontal) and addresses several additional research objectives such as the
use of multiple reference stations to achieve even more accurate solutions.
Director, Office of Operations Research and Development
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Technical Report Documentation Page
|1. Report No. FHWA-HRT-05-053
||2. Government Accession No.
||3. Recipient's Catalog No.
|4. Title and Subtitle
High Accuracy-Nationwide Differential Global Positioning System Test and Analysis Phase II Report
|5. Report Date
|6. Performing Organization Code
Dr. Benjamin Remondi, XYZs of GPS, Inc.
|8. Performing Organization Report No.
9. Performing Organization Name and Address
XYZs of GPS, Inc.
P.O. Box 37
Dickerson, MD 20842
|Desert Research Insitute
2215 Raggio Parkway
Reno, NV 89512
|Iowa State University
3025 Agronomy Hall
Ames, IA 50011
215 Fuller Road
Albany, NY 12203
|Pennsylvania State University
110 Technology Center
University Park, PA 16802
|University of Utah
819 William C. Browning Bldg.
Salt Lake City, UT 84112
|Cooperative Program for Operational Meteorology, Education and Training (COMET®) |
PO Box 3000
Boulder, CO 80307
|10. Work Unit No.
|11. Contract or Grant No.
12. Sponsoring Agency Name and Address
Federal Highway Administration
Turner-Fairbank Highway Research Center
6300 Georgetown Pike
McLean, VA 22101-2296
|13. Type of Report and Period Covered
Final Report 2001-2003
|14. Sponsoring Agency Code
|15. Supplementary Notes
The Contract Officer's Technical Representative, on this document was James A. Arnold, Research Electronics Engineer
The High Accuracy-Nationwide Differential Global Positioning System (HA-NDGPS) program focused on the development of compression and broadcast techniques to provide users over a large area wit very accurate radio navigation solutions. The goal was achieve 0 cm in real time over 322 kilometer baselines.
The focus of the Phase II effort was on several aspects of HA-NDGPS to refine the navigation solution and demonstrate its usefulness. To that end this report provides a description and analysis of these tasks as well as conclusions reached. The tasks include:
- Provide a basic examination of the utility of using data from two reference stations.
- Develop and implement a prebroadcast integrity algorithm.
- Develop interface software for various brands of GPS receivers.
- Rewrite the modular software.
- Evaluate lower baud rate messages more than once every epoch.
- Demonstrate driver analysis based on the HA-NDGPS navigation solution.
- Examine multipath noise levels at the Hagerstown, MD facility.
The approaches and results provided in this report offer significant insight into the success of the overall HA-NDGPS program and its approach to meeting the needs of many users.
|17. Key Words
Global Positioning Systems, GPS, Nationwide Differential Global Positioning System, NDGPS, Carrier Phase, long baseline, multiple reference station.
|18. Distribution Statement
No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161.
|19. Security Classif. (of this report)
|20. Security Classif. (of this page)
|21. No of Pages
|22. Price |
Form DOT F 1700.7 (8-72) Reproduction of completed pages authorized
TABLE OF CONTENTS
LIST OF FIGURES
- Figure 1. Map of South-Central
PA showing Hawk Run, PA; Hagerstown, MD; and Orbisonia, PA. The latter test
site is approximately 80 kilometers (km) from the reference stations.
- Figure 2. North component determined from HAG1 (black) and
HRN2 (red), and the weighted average solution (green).
- Figure 3. East component determined from HAG1 (black) and
HRN2 (red), and the weighted average solution (green).
- Figure 4. Height component determined from HAG1 (black)
and HRN2 (red), and the weighted average solution (green).
- Figure 5. North component versus east component cross plot
determined from HAG1.
- Figure 6. North component versus east component cross plot
determined from HRN2.
- Figure 7. North component versus east component cross plot
of HAG1 HRN2 combined.
- Figure 8. Antenna configuration on van used for collecting
data broadcast from HAG1 and HRN2 simultaneously. The van is equipped with
one GPS marine antenna and two demodulator receiver antennas.
- Figure 9. An example screen shot of prebroadcast positional
integrity with the correct site coordinates.
- Figure 10. An example screen shot of prebroadcast positional
integrity with the wrong coordinates.
- Figure 11. An example screen shot of prebroadcast measurement
integrity. The four columns to the right show the difference between raw measurements
and what is about to be broadcast. 16
- Figure 12. Demonstrated proof that GRIM to RTCM 18/19 works.
- Figure 13. Percentage of data collected 0 to 10 seconds
for 25 epochs.
- Figure 14. Expected HA-NDGPS performance at 180 km.
- Figure 15. Comparing 5-second broadcast with 1-second broadcast
- Figure 16. Comparing 10-second broadcast with 1-second broadcast
- Figure 17. Comparing 15-second broadcast with 1-second broadcast
- Figure 18. Comparing 20-second broadcast with 1-second broadcast
- Figure 19. Map segment of test site along U.S. Route 15
north of Frederick, MD.
- Figure 20. Display of nine tracks driven on U.S. Route 15
north of Frederick, MD.
- Figure 21. Display of defined "road map" created from nine
tracks in Figure 20.
- Figure 22. Representation of driver cross-track (i.e., left/right)
driving variation for the 9 loops associated with figures 18 and 19.
- Figure 23. Van configuration used for driver analysis on
U.S. Route 15.
- Figure 24. The Hagerstown GWEN site with a pentapod marine
antenna 4 to 5 meters above the hut to search for the cleanest signals.
- Figure 25. Van configuration for multipath testing at the
Hagerstown GWEN site for the NDGPS 700829 (3) antenna from Ashtech to van
700829 (3) antenna from Ashtech test.
- Figure 26. NDGPS 700829 (3) antenna from Ashtech to van
700829 (3) antenna from Ashtech initial convergence.
- Figure 27. NDGPS 700829 (3) antenna from Ashtech to van
700829 (3) antenna from Ashtech steady state with integers fixed.
- Figure 28. Van configuration used for multipath testing
at the Hagerstown GWEN site. In this case, HA-NDGPS marine antenna to van
marine antenna is under test.
- Figure 29. HA-NDGPS marine antenna to van marine antenna
- Figure 30. HA-NDGPS marine antenna to van marine antenna steady state with integers fixed.
LIST OF TABLES