摘要:

AbstractSpecialized tablesmaking possible time or longitude determination by lunar distances were eliminated from theNautical Almanacin the early part of this century. However, in an emergency, the present day navigator's tables can readily be used for this purpose. Either the altitudes of the moon and another body or the arc between the moon and another body near the same vertical circle are observed. Examples are given which can be followed by the practicing navigator. These methods and a plotting method which Sir Francis Chichester recently described1are analyzed for accuracy and convenience. Most of the observational accuracy can be preserved except that the plotting is difficult. It is shown that when the azimuths of the two bodies are close or when the bodies are near the same vertical circle, certain complicating observational errors and corrections and the great sensitivity to precise knowledge of latitude are minimized. There are “null” azimuths to be avoided. A sextant accuracy for the readings of 0.2′ and tables to the closest 0.1′ should at best give an RMS longitude accuracy of ±13′, and this is borne out i

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb01836.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractTo find two unknownsL, the latitude, and λ, the longitude, two equations are required. The navigator constructs the navigational triangles of two stars and obtains two equations forLand λ. Unfortunately it is almost impossible to solve these equations forLand λ, because of the difficulty of separating theLterms from the λ terms. I consider here the case where the navigator constructs the navigational triangles of three stars and so obtains three equations involvingLand λ. If the two time intervals between the measurements of the altitudes of the three stars are small enough one obtains a set of three equations from whichLand λ can be easily found with reasonable accuracy. If this accuracy is not good enough another set of three equations can be obtained from whichLand λ can be found by the method of Successive Approximations, §9. This method gives good accuracy even if the time intervals are not so small.Many modern calculators can perform arithmetical and trigonometrical operations of great complexity. Some can carry out programs of prescribed operations many times over. Such calculators can perform all the computations required in the methods briefly described above and can relieve the navigator of all the tedium of comp

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb01837.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractAgeneral descriptionof the Autoneties two‐frequency Omega receiver processor will be presented with emphasis on how calculator MOS/LSI circuitry has been applied to the automatic processing of Omega signals. The system functions and features will be outlined along with the method of operatio

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb01838.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractCURRENTLY, THE RESEARCH TRIANGLE INSTITUTE is under contract to NASA to provide support in evaluating OMEGA phase data being collected by NASA personnel. Phase data from Norway, Trinidad, and North Dakota are being recorded at all three OMEGA frequencies at various locations within approximately 500 km (300 n.mi.) of Hampton, Virginia. At most of the receiver sites modal interference of the North Dakota signal has been observed. Previous studies indicate that modal interference generally is significant only within approximately 1500 km of the transmitter, is more prevalent at night, usually is more predominant at 13.6 kHz than at 10.2 kHz, and generally manifests itself as a shift in the average phase measurement at a given receiver site. The temporal effects of modal interference other than the presunrise phase shift have not been reported and apparently are only rarely experienced.This paper discusses time varying modal interference experienced during several phase measurement periods in the winter of 1973–1974. Interference was observed at different receiver sites all located approximately 2 Mm from North Dakota. Large temporal phase fluctuations were noted in the nighttime phase measurements on several occasions. Average nighttime phase levels in some cases corresponded very closely to the daytime values over large portions of the nighttime period. In other cases this occurred for approximately two hours between the middle of the nighttime period and sunrise. In still other cases the shift from the normal nighttime level to near daytime level and back has been more sinusoidal with a period of from one to four hours. There have been isolated situations when peak to peak fluctuations have been on the order of 50 cec and greater. Amplitude fluctuations generally accompany these large phase fluctuations. In some cases modal interference during the daytime has appeared as a more conventional level shift with little time variation.An analysis of these temporal phase perturbations due to modal interference is presented using a theoretical model. Conditions which may have caused this interference at these relatively long distances from the transmitter are discusse

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb01839.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb01840.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractAn analysis of the errorcomponents of standard distance measuring equipment (DME) is presented, with emphasis given to the dependence of noise and bias‐type errors upon signal strength. The analysis is based upon lab measurements of equipment performance, static transponding experiments, and flight test data. An ARN‐84 military TACAN set was used with F. A. A. maintained ground stations in the Northeastern U. S. The largest single error component in the system is found to be the variation from nominal of the average transponding delay in the ground station. This variation produces a mean ranging error which is dependent upon the strength of the interrogating signal; the nature of the dependence is in turn related to the type of equipment used at the ground station. The results of the error component analyses are assessed in terms of the design of accurate positioning systems which use

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb01841.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractCurrentLoran‐Cradio navigationequipment has demonstrated a repeatable precision index of less than 0.01 μs/km. Thus, two co‐located receivers measuring the same time difference will deviate less than this amount as to the standard deviation of their measured time difference. It is therefore concluded that operation of Loran‐C in a differential mode is a feasible technique for such practical matters as collision avoidance, instrument landing systems, air traffic control, precise location of surface vessels used out of sight of land in underwater exploration, and ground based vehicle location in the non‐urban environment. By differential operation mode, we mean that two vehicles can determine their distance apart, their rate of closing or separation, and indeed their direction of relative motion, if the measured time difference information on each vehicle is relayed between vehicles.Loran‐C can be compared quantitatively with other systems such as Omega operating in a differential mode. A comparison of Loran‐C data with the Beukers‐Nard Omega data reveals a possible 20 to 100 accuracy improvement factor if we use Loran‐C instead of Omega in the 0 to 700 km differential separation range. We conclude that the fundamental reason for part of the improvement is the reciprocal phase measurement improvement with frequency. The remainder of the improvement is a consequence of the greater stability of the pulsed ground wave propagation mechanism of Loran‐C as compared with the single frequency ionospheric waves of Omega. Frequencies greater than 100 kHz would give greater improvement with a loss of range or coverage area.We have found that Loran‐C is an excellent propagation measuring device for the detection and identification of effects of irregular, in‐homogeneous terrain in the spatial domain, and the study of meteorological variations in the time domain. Furthermore, the Loran‐C skywave signal can be used as a D‐region diagnostic to study particle precipitation events and D‐region variations with latitude, season and solar zenith angle.We make the observation from our Loran‐C studies that the first prerequisite to a capability for prediction of propagation phenomena is the ability to separate, identify, and understand the physical nature of the observed radio measurements. This prediction capability is essential to the successful operation of radio navigation systems in both the normal and the

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb01842.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb01843.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractSixteen pilots of two widelydifferent experience levels were flight tested in a Beechcraft Twin Bonanza on an area navigation task involving 3‐D approaches having two levels of navigation procedural complexity. Two types of displays were used for leveloff at MDA, command leveloff and an altimeter. The four recorded performance measures were vertical steering, horizontal steering, airspeed control, and procedural accuracy. The less complex approach procedures (Simplified) resulted in better performance on all four recorded measures than the more complex procedures (Standard). However, no reliable performance differences were evident between levels of pilot experience and types of leveloff displays. In comparison with previously assumed values of flight technical error, Standard Procedures generally yielded larger errors, and Simplified Procedures generally smaller error

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb01844.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb01845.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY