摘要:

Abstractthe coverage and availability offered by the OMEGA radionavigation system make it a natural choice for search and rescue systems that are to operate globally. Effective use of OMEGA signals in these applications requires ambiguity resolution beyond the 132 km lanes provided by the present three frequency format or the 528 km lanes provided by the proposed four frequency format. Additional ambiguity resolution can be provided by a variety of techniques based on information already present in the OMEGA signals, but not used in conventional navigation receivers. These techniques make use of envelope time‐of‐arrival, signal strength, dispersion, multiple intersection, unique frequencies, and direction of arrival. Use can also be made of other low‐frequency signals, including VLF communications, Loran–C envelopes, and sferics. This paper reviews the capabilities and limitations of each technique. On the basis of work done to date, it appears that a combination of techniques can provide complete ambiguity resolution in most sit

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb01340.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe Rules of The Road, more properly known at the International Regulations For Preventing Collisions At Sea, have been the law of the maritime community in this country since 1895. The first Rules enacted by Congress in 1864 closely followed the British Rules. These Rules were re‐enacted in 1874, and superseded by the Rules of 1885. A Conference was held by the major maritime nations in 1895 and the first International Rules adopted. They became effective in 1897. (For an excellent discussion of the history and background of the Rules see Healy and Sharpe, Admiralty Cases and Materials.)Subsequent conventions were held, notably in 1946, 1960 and, most recently, in 1972. Few changes were made until 1960, when radar was officially recognized and Article 16(c) and the Annex to the Rules were adopted. Now, in 1972, we have a complete rewriting and regrouping of the Rules and important new responsibilities placed on the navigator. (The text of the 1972 Rules [72 COLREGS] is set out in 33 CFR and CG‐169, Navigation Rules, copies of which are available from the Superintendent of Documents, Government Printing Office, Washington, D.C., 20402.) An excellent discussion of the 1972 Rules which took effect July 15, 1977 may be found in a series of articles by Radm W.W. Barrow and Cdr. J.M. Duke. These articles were published in the Proceedings of the Marine Safety Council from September 1973 through February 1974. The authority of these articles is greatly enhanced by the fact that the authors, and Commander Duke in particular, were closely associated with the preliminary studies in this country and in the final work of IMCO in London. This article will not attempt a broad coverage of the new Rules but will concentrate on the Rules covering navigation in poor visibility, the use of radar, and a proper look

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb01341.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractWith the increase in the number of users and potential users of the Omega navigation system, caused in part by the scheduled shutdown of the U.S.‐operated Loran/A chains, there is a need to assess the performance of the Omega system. This is particularly true for those areas where little or no measurement data from the current permanent stations exists.This paper presents the highlights of the results of a validation of the Omega system over the Western Pacific area.Hourly averages of LOP phase measurement data taken over several months at seven fixed monitor sites located within the Western Pacific area were reviewed. These data were supplemented with data taken over the area by a dedicated flight test conducted by the U.S. Navy. In addition, several hundred operational Omega navigation observations provided by ship and aircraft crews were evaluated. Statistical analyses were performed on the data, the results of which were compared to predictions wherever possible. Summaries of the analysis results were reviewed, interpreted and structured in the form of tables and charts in order to present Omega performance guidelines with a reasonable degree of traceability to the basic measured data.Recommended sets of LOPs for regions within the Western Pacific area are presented along with alternate LOPs. Regions with marginal redundant coverage are identified. In addition, Omega coverage over those regions previously serviced by Loran‐A was examined for adequ

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb01342.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractAn orthogonal system of interferometry baselines aboard a geostationary satellite is considered for a variety of applications involving navigation, surveillance, and traffic control. The position determination is based on the relationship between the measured phase differences, the known and unknown transmitter positions and other systematic error model parameters using a generalized Least‐Squares estimation procedure.Study of the effects of the various system and error model parameters on the position accuracy reveals that the accuracy is critically dependent on the baseline length and on the magnitude of the random component of the measuring errors. With a 50‐m baseline, the obtainable accuracy at a frequency of 1.5 GHz is comparable to that of the NAVSTAR/GPS system. Several trade‐offs with respect to the system accuracies, the number of users, data rates, hardware costs, etc., are examined. Simultaneous utilization of the same communication channels for both navigation and data transfer is found feasible. Based principally on the equipment requirements of potential users, five candidate or “strawman” interferometer systems are configured.The overall performance of the interferometer system is considered excellent when compared with other existing or planned navigation systems. Considering the interest and needs of prospective users for a multicapability system, this interferometry system is considered potentially viable in meeting their req

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb01343.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractFull automation of non‐combatant shipping is now a certainty. It is almost just as certain that the full implications of this have not yet been faced; for some of them we should begin to prepare even now. For one thing, all shipboard control functions will be moved to the bridge. This includes those for navigation and maneuvering, the engines, and cargo operations. Crews will be markedly smaller. Bridge watchstanders will be hybrid deck‐engineer‐computer‐capable officers. Specialist skills will become even more the province of the warrant‐level technician. There will be little room for the unskilled on board ship. Watchstanders will have to be trained for their expanded roles, breaking down barriers between deck and engineroom that have stood for a hundred years. Computers—CPUs, dedicated micro‐processors, desk top and hand calculators—will reach into every corner and every level of activity. Right now, we most need to make the systems we have more reliable. MTBFs are much too short by far. MTTRs are too long. Standardization and modularization are a crying need. Additional reliability will have to be added, through redundancy if necessary. Self‐test will be a feature of all equipments. Defective parts will be replaced and either returned to depot for repair or simply thrown away. Supply and repair centers will have to be strategically located; servicing routinely will be by helicopter by under way teams wherever called for. Since we are talking mainly about people, lead time is

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb01344.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractA graph is developed which gives geometric dilution for fixes obtained hyperbolically using information received from three stations. Only bearings from the user to the stations are needed. The approach can be characterized as oriented to the user rather than to system development and is particularly valuable in assessing station choices in redundant systems such as Omega. Dilution is shown to be minor even if all bearings are in the same semi‐circle provided the central station is on a nearly central bearin

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb01345.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractFinding longitude by lunar distance observations with the formerly lengthy data reduction is simplified with a pocket calculator method described. Such calculators are coming into use for small boat navigation. In contrast to the recent lunar altitude methods using LOP constructions, which attracted navigators, it is free from the serious plotting and horizon inaccuracies. Because of the number of keystrokes, the calculator should use a recordable program. In the event of lost radio or chronometer time, the method can approach an RMS longitude accuracy of ±8 minutes

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb01346.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb01347.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb01348.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb01349.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY