摘要:

ABSTRACTPrecision navigation about a reference point using Loran‐C can be achieved by subtracting the Loran Time Differences measured at the reference point from the received Time Differences, thus reducing by common‐mode cancellation the effect of variations in signal propagation velocity; a potential application of this technique is aircraft final approach guidance. In addition to the classical Geometric Dilution of Precision, performance of Loran‐C in this “relative navigation” mode is limited by reference datum accuracy, by the response of the receiver's tracking loops to noise and vehicle accelerations, and by local deformations in the shape of the Lines of Position grid. Optimization of the receiver's tracking loop bandwidth can result in an expected performance of 45 meters (2‐σ) for a 0 dB signal to noise ratio and typical aircraft low‐approach maneuvering accelerations. Ground‐level measurements at this level of precision indicate the existence of a “grid microdeformation”: localized, repeatable distortions of the Lines of Position over distances much smaller than the carrier wavelength. It is concluded that 2‐σ horizontal accuracies of 100 meters or less are realistically achievable with relative Loran‐C if signal to noise ratio and maneuvering acceleration limits are specified. This accuracy is significantly better than that of VOR or NDB approach systems, but not as

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1985.tb00887.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTThe Bi‐normal density distribution function on a surface is represented by a position vector and covariance matrix. Its physical dimensions are described by the error ellipse. A generalized scalar is the radial or circular error which denotes the probability within a radius of the position. To compute the radial error probability (or probability circle) precisely, a non‐trivial numerical integration is necessary. Simpler but less accurate conventions in common use are the Drms and CEP. The error ellipse semi‐major axis is also sometimes applied to radial error. These three measures of radial error are subject to variations in probability as a function of the eccentricity of the distribution. The probability of a circle can be obtained simply and more accurately by the use of a third order polyn

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1985.tb00888.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTThe technique of estimating a vessel's speed over the ground by measuring the Doppler frequency shift of an acoustic pulse reflected from the bottom has been successfully employed by the oceanographic community for many years. A system based on this principle may act as a precise dead‐reckoning navigation device, or may provide an accurate velocity reference for other types of navigation systems. Despite the history of success of the Doppler sonar to date, improvements in marine technology and more stringent operational requirements have placed new demands on system accuracy. The study of Doppler sonar navigator error growth and error prediction suggests that significant improvements in the performance of existing systems may be achieve

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1985.tb00889.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTThis paper describes an investigation of the use of the Global Positioning System (GPS) to calibrate an instrumentation radar. An existing calibration program called STARCAL was used to perform computer simulations. The accuracy of STARCAL is used as a comparison as well as a guide to design simulation scenarios. It is shown that for a comparable calibration accuracy, the proposed procedure would require many hours to complete. Based on this and other findings, it is concluded that the proposed method is not practical. However, it is recommended that measurements be made to ascertain the true radar cross section (RCS) of the GPS satellites and the variation of it, so that a future analysis can be made to refine the current findings.

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1985.tb00890.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTThe emergence of data bases for the management of hydrographic data raises some questions about how to characterize the quality of data placed in the data base. This is important, since subsequent automatic handling of the data will be less dependent on the human “feel” for data quality that has been the case in the past.In this paper we review approaches that can be taken to obtain data quality parameters for navigational data. In particular, those based on various statistical assumptions are described and compared. Proposals for various options are presen

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1985.tb00891.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTA fundamental method of calculating the time difference between meridian transit and when a body is at its highest altitude allows direct correction for the effects of vessel velocity and rate of declination change. A novel graphical procedure for determining the time of highest altitude results in a simple way to obtain a fix from observations near meridian passage. Calculators or computers are not needed in the method. An example demonstrates the practical merit of the approach. Derivation of the equations is presented, and observational error sensitivity is discussed.

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1985.tb00892.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1985.tb00893.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY