Title

DGPS availability and accuracy in a harbor area

Document Type

Conference Proceeding

Date of Original Version

11-22-2004

Abstract

The Coast Guard currently operates a maritime differential GPS service consisting of two control centers and over 85 remote broadcast sites. This service broadcasts GPS correction information on marine radiobeacon frequencies to improve the accuracy and integrity of GPS. The stated accuracy is 10 meters in all coverage areas with typical accuracy much better than this. However, to date there has been no quantitative analysis of the absolute accuracy possible in a post-SA environment. The Federal Aviation Administration (FAA) has developed an alternative system for augmenting the GPS system called WAAS or Wide Area Augmentation System. This system transmits corrections from one or more geostationary satellites that can also act as additional pseudo-GPS signals to provide an additional pseudorange for position solutions. This system was developed for aeronautical users, but should be able to be used by maritime users as well; however, to date no definitive study has been done of availability for a maritime user. With sponsorship from the Coast Guard C2CEN, the Coast Guard Academy has undertaken a study of the Availability and Accuracy of DGPS and WAAS in a harbor environment. The goal of this study is to determine DGPS beacon and WAAS coverage (signal strength and availability) and absolute accuracy in certain harbor areas. The testing will be conducted in two parts: static and kinematic. The static testing will consist of an equipment suite designed to collect DGPS signals from 4 different beacons, WAAS GPS, and unaugmented GPS from a fixed location. The Continuously Operating Reference Station (CORS) System will be used to postprocess the GPS information for each fixed location to provide a highly accurate ground truth position which can be used to calculate statistics on the error in the DGPS and WAAS positions. Data will be collected at multiple locations around the harbor. The kinematic testing will consist of a suite of equipment installed on a vessel to collect DGPS beacon and WAAS signal strengths as the vessel traverses the harbor area. This paper presents data collected in the New York harbor area, along the Eastern seaboard, and the Miami, FL area in the Fall of 2003 and January 2004. DGPS and WAAS availability within the harbor is shown. Statistics on the DGPS and WAAS position errors are presented for each beacon tracked, and at each location around the harbor.

Publication Title

Proceedings of the National Technical Meeting, Institute of Navigation

Volume

2004

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