摘要:

ABSTRACTThere have been numerous papers published on GPS integrity monitoring from the perspective of detecting and mitigating the effects of space segment failures. Another important aspect of GPS signal integrity that has received less attention is the monitoring and mitigation of radio frequency (RF) interference, which can result in degraded accuracy performance or complete loss of receiver tracking.This paper describes RF interference monitoring and mitigation techniques that have been developed for military GPS receiver applications where intentional jamming must be anticipated. RF interference analysis techniques are also presented. These techniques should be considered if RF interference becomes a source of GPS signal integrity problems for civil avionics applications.

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1994.tb01886.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe Federal Aviation Administration (FAA) Satellite Program Office is developing a GPS Wide‐Area Augmentation System (WAAS) to support a precision approach capability down to or near the lowest Category I (CAT I) decision height (DH) of 200 ft. In one of the candidate architectures under development, a vector of corrections is sent to the user via geostationary communications satellites (e.g., Inmarsat). This correction vector includes components for ionospheric, clock, and ephemeris corrections. The purpose of this paper is to evaluate the performance of the grid‐based algorithms and other real‐time ionospheric algorithms that could be implemented at the ground ionospheric reference stations, as well as at the airborne receiver. Results show that all of the ionospheric algorithms used in this paper (grid‐based, least‐squares, and spherical harmonics) provide roughly equivalent performance. Based on an extensive data collection program, the error in estimating ionospheric delay is derived. An analysis of WAAS accuracy performance is also

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1994.tb01887.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTGPS receiver dynamic tracking error is an often misunderstood concept. Flight test results and field experiences have shown dynamics‐induced errors that can be related directly to the receiver architecture. To evaluate the effects of multipath in airborne receivers, it is necessary to isolate multipath from receiver tracking errors. Separation of multipath and receiver tracking errors can be difficult, particularly for a highly dynamic receiver platform. This results from the fact that the two error sources can be similar in magnitude and frequency. Historically, receiver dynamic tracking error has often been ignored or overlooked when analyzing multipath data. This paper describes a controlled experiment that allows for the isolation of multipath and receiver tracking errors. The theory behind the dynamic tracking error phenomenon is described, along with the isolation technique. Data collection and analysis results are presented to confirm the viability of the techniqu

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1994.tb01888.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe electronic chart display and information system (ECDIS) is a navigation tool that superimposes electronic chart, ship's position, and radar information on one display. The purpose of the test described in this paper was to compare baseline performance (i.e., a mariner using traditional techniques of a paper chart, radar/automated radar plotting aid (ARPA), and visual piloting) and performance with ECDIS. Evaluation criteria included safety of navigation, reduction of navigation workload, mariner comfort with chart features and navigation functions, and integration of radar features.Results indicated that when using ECDIS with radar overlay, the average workload was the lowest, leaving more time for collision avoidance. The mariners reported close agreement with the features and functions required by the International Maritime Organization/International Hydrographic Organization (IMO/IHO) Draft Performance Standard for ECDIS. Statistical analyses performed showed navigational method, visibility, and the presence of a radar overlay to be the most significant factors for improving navigational performance.

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1994.tb01889.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThis Federal Highway Administration (FHWA)‐sponsored operational test will evaluate the use of GPS (location) and cellular phone (two‐way communications) to provide assistance to travelers in an emergency dispatch area of more than 12,000 m2in central Colorado. The test will implement 2,000 in‐vehicle units using a low‐cost GPS location device.The major objectives of the operational test are to evaluate the impact of the system and response network on emergency response activities and time, and public safety; to evaluate a low‐cost system that allows users to request roadside assistance; and to identify the necessary structure, responsibilities, and service levels of a travel assistance center for commercial operation of the system. The operational test Mayday service will first become available to travelers in mid‐1995. The system architecture to be implemented and the operational test program are described in

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1994.tb01890.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTDuring 1992, members of the FAA Navigation Satellite Operational Implementation Team (SOIT) developed the requirements for Technical Standard Order (TSO) C‐129, which describes capabilities of GPS avionics to be used as a supplemental means of navigation for en route through nonprecision approach phases of flight. During the writing of TSO C‐129, the SOIT requested that analyses of certain issues be performed, including the effect of certain types of altimeter aiding on receiver autonomous integrity monitoring (RAIM) availability, and the risk of continuing flight in the event of an unpredicted loss of RAIM after an aircraft crosses the final approach fix (FAF) of a nonprecision approach. This paper summarizes technical analyses used in the development of these requirements.The results showed that altimeter aiding significantly improved RAIM availability, and that the risk of continuing an approach in case of an unpredicted loss of RAIM under certain conditions was acceptable. Operational and technical considerations, including the results of these analyses, led the SOIT to require certain capabilities of GPS avionics to be covered under TSO C

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1994.tb01891.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTTo decide whether a desired maneuver can or cannot be undertaken safely, a prudent navigator must be aware of both the current spatial uncertainty of the vehicle's positioning system and the spatial uncertainty of the navigational map model being used to depict the theater of operations. This paper discusses the electronic chart (EC) implications of both GPS vessel positioning errors and the relatively large data modeling errors specific to bathymetric map models (charts). It proposes and demonstrates software solutions that statistically evaluate both of these spatial uncertainties and graphically integrates the two stochastic models within an EC environment. The depicted estimates of bathymetric map model errors were computed using a modified kriging algorithm that interpolates both a gridded seafloor model and astochastic surfacethat describes the fidelity of this model. This algorithm is being developed as part of an international effort to define quality standards for digital bathymetric data. The paper also describes how GPS real‐time position error estimates were validated experimentally, and how enhancements to the estimation algorithm were devise

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1994.tb01892.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY