摘要:

ABSTRACTCelestial navigation represents the most accurate traditional method of fixing a ship/aircraft geographic position. One of the more time‐consuming efforts involved in celestial navigation occurs when reduction tables are entered to obtain the azimuth and altitude corrections to the assumed position. In addition, opportunities for error increase when tables are used, compounded with increased probability of mistake when plotting numerous lines of position from various origins. When multiple star observations are taken, the time required on the part of ship/aircraft navigator can be considerable.A quick, accurate method for calculating lines of position from a single assumed position has already been developed. The procedure to reduce these lines of position to a most probable fix position will be discussed within this pape

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01435.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01436.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTCollision avoidance aids used in conjunction with marine radar range from plotting sheets and special plotters to computer based “Automatic Radar Plotting Aids” (ARPA). One device, which has received very little attention is the hand‐held or pocket calculator. The potential of the calculator for use in radar tracking is explored. The use of calculators with differing capabilities are examined respecting their possible use for distance/velocity/time computations, vector arithmetic to determine relative and true motion and, with the more advanced programmable variety, solutions for closest point of approach (CPA) information as well as an aid in maneuvering to avoid targets whose CPA's are too close. An example of an algorithm for a programmable calculator is presented. The limitations of calculators as a collision avoidance aid are discussed. The conclusion is that the available hand‐held calculators will not replace ARPA's but could be useful as a backup to ARPA and as an aid on ships not equipped with ARPA when traffic density is not so great that the operator becomes ove

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01437.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTIn 1975 the United States Coast Guard began a project to improve the positioning of aids to navigation. This paper describes the traditional positioning methods in comparison with the newly developed analytical technique. The marine sextant remains the basic instrument used in positioning, and horizontal sextant angles are the input to the computer‐driven proces

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01438.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTThe accuracy of navigational fixes obtainable with present day navigation systems is such that the Earth's geodesy must be considered, especially in comparing relative fixes. Approximations to the exact transformations between geodetic and geocentric coordinates can be made so as to optimize computer times. This paper presents the results of a systematic error analysis of these approximations to the exact coordinate transformations and the resulting real‐time and core requirements on an AN/UYK‐20 standard Navy mini‐com

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01439.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01440.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTThe classical problem of celestial navigation, in its simplest form, is the determination of an observer's longitude and latitude from the altitudes of two identified stars, observed at a known Greenwich Mean Time on a known date. A novel solution of this problem in closed analytical form is given herein. The solution yields the two possible positions of the observer without any prior knowledge of his position, without any dependence on tables of computed altitudes and azimuths for an assumed position, and without any graphical work. The basic two‐fold ambiguity is resolved to yield a single, unique position by repeating the calculation using the altitudes of a third star and of one of the two previous stars. The full analytical solution is given as are some artificial numerical examples, readily performed on a hand‐held, programmable calcula

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01441.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTThe method described is a single program method developed for a Texas Instruments SR‐52 programmable hand‐held calculator, but it can also be easily used on any other programmable calculator of the same or higher capacity. It provides a direct solution for latitude and longitude of the observer's position from simultaneous or non‐simultaneous observations of two celestial bodies (either the Sun, Moon, planets or stars), as well as from a double observation of one body (usually the Sun, which until now has been practiced by advancing the earlier position line to the time of the last observation), even for cases where the second observation is close to or exactly on the observer's meridian. The coordinates of the fix are obtained directly on the sphere as the intersection of circles of position without the need to draw a diagram of the situation in the sky in order to decide what to do with calculated parameters, and thus obviating the necessity to determine position lines (intercepts and azimuths) by Marcq St. Hilaire method.In addition, the same program enables also the computation of intercepts and azimuths (position lines), and thus satisfies those navigators who prefer the St. Hilaire method of solution or want to use it for checking of the direct m

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01442.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTThree methods for obtaining a two body fix are presented. For practical use a calculator with magnetic card capacity is necessary. Advantages of the methods are: One simple rule covering all positions is sufficient to avoid ambiguity, the methods can be used in all positions, an approximate position is not necessary, and the fix is calculated directly. One method employs rotation of a spherical triangle and two methods are based on vector calculation.

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01443.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTA proof is given that the effects of the height of the eye, earth curvature, and atmospheric refraction can be safely ignored when vertical sextant angle measurements short of the horizon are used in practical navigation problems. The expressionDtan(hs) =H, relating the distance‐off, sextant altitude, and navigation aid height, is shown to provide satisfactory accuracy for safe navigation where dip short of the horizon techniques are applicable. The double table entry procedure suggested in Bowditch for vertical sextant angle calculations is shown to be unnecessary and is incorrect with respect to the prediction of the effects of both earth curvature and atmospheric refractio

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01444.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY