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Coordinating, Developing, and Delivering Highway Transportation Innovations

This report is an archived publication and may contain dated technical, contact, and link information
Publication Number: FHWA-HRT-05-034
Date: July 2005

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.

Toni Wilbur
Director, Office of Operations Research and Development


This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This report does not constitute a standard, specification, or regulation.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

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Technical Report Documentation Page

1. Report No. FHWA-HRT-05-034 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
July 2005
6. Performing Organization Code
7. Author(s)
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
16. Abstract
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

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