摘要:

ABSTRACTIn August 1992, six European nations—Denmark, France, Germany, Ireland, The Netherlands, and Norway—signed an international agreement to establish a Loran‐C system covering North‐West Europe and the North Atlantic Ocean. The system will comprise nine stations (six existing and three new), arranged in four chains. In estimating the coverage this system will provide, the effects of signal attenuation, atmospheric noise, carrier‐wave interference, skywave propagation, the change of envelope‐to‐cycle difference with range, and transmitter timing uncertainty have all been taken into account. Contours of repeatable accuracy have been predicted for conventional hyperbolic receivers, and for receivers that work in the newer semicircular, cross‐chain, and master‐independent modes. This paper explains the coverage prediction process and the assumptions made. It presents details of the final configuration of stations chosen from a number of alternatives and shows the predicted performance

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1993.tb02305.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTA navigation sensor integration architecture is proposed to improve navigational reliability and accuracy on vessels having two inertial navigators plus other aiding sensors, such as GPS, Loran‐C, Omega, and speed log. This hierarchic alliance of Kalman filters is a systematic structure of dynamically configured parallel filters, sharing measurements but not state information. Unlike a centralized, or even a federated architecture, this scheme can always provide an uncorrupted optimal solution, even after the occurrence of a subtle sensor or software fault that was not immediately detected. Thus it substantially simplifies reconfiguration and eliminates the need to “back out” of a failure. It also facilitates the detection and isolation of sensor and software faults by allowing an additional level of tests, which use sensitive intrafilter fault detection techniques with interfilter fault isolation. These techniques are investigated using high‐fidelity simulations and sea trial data, with encouraging

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1993.tb02306.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTDemonstrations of GPS‐based approach and landing systems have caused many potential users of the Microwave Landing System (MLS) to question whether it is appropriate to install such a costly system. An investigation of the resistance to electromagnetic interference of Standard Positioning Service (SPS) C/A‐code GPS receivers in aviation environments demonstrated their susceptibility to inband noise; for example, 1 W of radiated power jammed an airborne receiver at ranges in excess of 30 km. Although resistance to out‐of‐band interference is significantly greater, transmissions from communications systems in frequencies adjacent to the GPS bands present considerable problems for GPS reception. Consequently, the use of C/A‐code receivers for applications requiring high reliability and integrity, such as approach and landing, must be q

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1993.tb02307.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTProposed solutions to the GPS integrity issue generally focus on means of reliably determining when GPS deviates from some standard of performance acceptable to a given user group, and warning that group not to use the service. One of the key elements in the development of any reliable GPS integrity response system is an understanding of how GPSnormallyperforms. To support that need, this paper examines the performance of the current Block II satellite constellation from a time‐ordered and a statistical behavior perspective. The paper begins with a general discussion that relates GPS accuracy characteristics to the integrity problem. The time‐ordered behavior of GPS position solution errors is then described, and error behavior dependencies on user location are defined. The paper then develops GPS range and position error statistical distribution characteristics. Finally, the results of the time‐ordered and statistical behavior analyses are assessed in terms of their implications for the GPS integrity monitoring and response pr

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1993.tb02308.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTThis paper describes a multiple‐reference‐station DGPS system using a geostationary satellite‐based data link. The role of multiple reference stations in improving DGPS accuracy is discussed. Operational multiple‐reference‐station DGPS results are presented. They are compared with standard DGPS results on short and long baselines. The results demonstrate the system capability of maintaining 2.5 m (1‐sigma) horizontal position accuracy (about the mean error) at long distances up to 1000 km from the referen

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1993.tb02309.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTConventional differential GPS (DGPS) systems operate on the principle that the two main error sources (i.e., the satellite ephemeris and the atmospheric delay) are spatially correlated. Pseudorange measurements made at precisely located reference stations are compared with corresponding ranges computed from the known coordinates, and the errors derived are transmitted as differential corrections for application by DGPS users within range. The drawback of such systems is the limited range over which the differential corrections are valid, due to the rapid decorrelation of the error sources with increasing distance from the reference station to the user.This research and development study has led to the development of a wide‐area DGPS (WADGPS) system design, which will generate corrections for users over a large portion of the earth. The system is based on a limited number of reference stations, which are sufficient to spatially model the ephemeris and atmospheric errors. The resulting corrections have been found to lead to accuracies comparable to those obtained by conventional DGPS, with no dependence on the distance between the user and reference site

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1993.tb02310.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTPrecise kinematic differential positioning using GPS requires the use of carrier phase observations with correctly resolved integer ambiguities. On‐the‐fly (OTF) ambiguity resolution, i.e. ambiguity resolution while the receiver is in motion, is desirable, since it increases the flexibility and reliability of the kinematic positioning. It is, however, not an easy task. Several factors must judiciously be taken into consideration. One of these is a fast and reliable OTF ambiguity resolution technique. OTF ambiguity resolution techniques generally resolve ambiguities by testing many combinations of ambiguity sets or positions representing the ambiguity sets inside a certain predetermined searching space. The shape and size of the searching space affect the speed of ambiguity resolution.In this paper, the construction of the optimal searching space is explained and discussed, and results based on a static zero baseline GPS data collection are presented. It is shown that for fast and reliable ambiguity resolution, the ellipsoidal searching space should be used instead of the cube. Moreover, the searching space should neither be too small nor too la

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1993.tb02311.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

From Sails to Satellites (The Origin and Development of Navigational Science). J.E.D. Williams

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1993.tb02312.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY