The U.S. Coast Guard has a research program to investigate the capability of C/A-code GPS and methods to improve its accuracy and integrity. A differential GPS demonstration system is being assembled and tested at the U.S. Coast Guard Research and Development Center in Groton, Connecticut. Analysis of static and dynamic testing is discussed. Details of instrumentation supporting the test program are also presented. BACKGROUND
Real‐time differential GPS is fundamentally limited by a) signal estimation errors, b) satellite ephemeris errors, c) propagation decorrelation errors, and d) local multipath errors. In this paper we address the latter two error sources. An understanding of these is needed to establish an error budget for any monitor station network that the U.S. Coast Guard would consider for a nationwide system. To estimate these error sources, extensive two‐frequency P‐code and integrated Doppler data have been collected over 150 kilometer and 1500 kilometer baselines. A processing scheme is developed which employs both code and carrier observations. Applicable to real‐time differential systems, as well as to post‐collection data analyses, the estimation scheme treats multipath errors and carrier‐code offsets as state‐variables. The resulting Kalman filter yields the very precise carrier observation, corrected for carrier‐code offset. Day‐to‐day repeatability of multipath errors is illustrated. The decorrelation of ionospheric errors across short and long baselines is evaluated by combining the integrated Doppler estimation scheme with the standard two‐frequency ionospheric measurement technique. Also discussed are the impact of multipath and ionospheric error sources on Differential GPS.
Automated Dependent Surveillance or ADS is an improvement to current Vessel Traffic Service (VTS) operations and a step towards a "voiceless VTS." The two main requirements for an ADS system are an accurate position sensor on the vessel and a communications link between the vessel and the Vessel Traffic Center (VTC). The first is satisfied by the operational United States Coast Guard Differential GPS (DGPS) service. The second has been the subject of recent research. Three existing communications technologies were evaluated and tested: Advanced Mobile Phone Service (AMPS) cellular, VHF-FM Digital Selective Calling (DSC), and Newcomb L-Band Satellite. These communications methods were tested in the Narragansett Bay Rhode Island area and evaluated according to the following criteria: coverage area, reliability, integrity, reporting interval, latency, and cost. Of the three communications methods, the DSC and Newcomb Satellite technologies were found to be well-suited for ADS implementation. ' Coverage is now provided by Cellular One of RYSNET (A-side) and Bell Atlantic Nynex Mobile (B-side) 131. The opinions or assertions contained herein are the private ones of the authors and are not to be construed as official or reflecting the views of the Commandant or the Coast Guard at large. 0-7803-3519-8/96 $5.00 0 1996 IEEE
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.