摘要:

ABSTRACTFully automaticOmega navigation systemshave been demonstrated and are beginning to be used operationally in aircraft and other vehicles. A natural question is the accuracy achieved by such systems. Concern over the probability of maintaining correct lane identification complicates this question. Use of the root‐mean‐square (rms) statistics is shown to be a misleading measure of operational performance. Alternate methods of specifying the navigational errors of automatic Omega navigators are discussed. Cumulative percentile plots are recommended for the specification of errors. Use of Weibull probability paper to study radial error trends is demonstrated. Illustrations of error analysis techniques are given, based on actual Omega flight test d

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb00718.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

ABSTRACTIn anAcousticTranspondernavigation system the vehicle position is determined in relation to the transponders by the use of ranges to the transponders and the distances between transponders. The vehicle position determined is usually inaccurate due to the timing error and inaccuracy of the sound speed assumed in obtaining the range data. This paper develops computational algorithms for the optimal estimation of vehicle position with given erroneous range data.The development begins with the formulation of a least‐squares error criterion. Computational algorithms are then developed to best estimate the vehicle position by minimizing the least‐squares error criterion. For the moving vehicles, optimal filtering algorithms are developed which sequentially update the vehicle position based on the knowledge of the vehicle dynamics and the range measurements. Computational results for one illustrative example in the application of optimal filtering algorithms are presen

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb00719.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

ABSTRACTThe research triangle instituteunder contract to NASA is currently evaluating phase data recorded at all three OMEGA frequencies by NASA personnel at various locations throughout Virginia, North Carolina and Maryland. Of particular interest is the development of the ability to predict differential OMEGA error in terms of the various factors which influence this error. Previous studies have indicated that differential OMEGA can offer significant navigation accuracy improvement over ordinary skywave corrected OMEGA. Two major sources of uncorrected differential error which have been identified are geometric dispersion error and statistical decorrelation error. Geometric dispersion error is peculiar to the uncorrected differential operation whereas statistical decorrelation error is not. Statistical decorrelation error has previously been analytically formulated in terms of differential receiver displacement range.In this paper, primary emphasis is placed on the analytical determination of parameters affecting uncorrected differential OMEGA error and their relative importance. For example, within the differential region around a base receiver station, differential error is dependent on range and azimuth from the user receiver to the base receiver for any given line of position (LOP). Regression analysis techniques are employed to process large amounts of collected OMEGA phase data in the differential region around Hampton, Virginia. Results show analytically the sensitivity of the mean and standard deviation of differential OMEGA error to variations in parameters such as separation range and azimuth, time of day, season, weather conditions, frequency, etc. Confidence in results is evaluated numerically and used to indicate additional data needed to improve prediction confidence. The ability to predict differential OMEGA error within a given region can significantly improve the practical utility of this form of navigation.

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb00720.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

ABSTRACTUnder a continuing programsponsored by the Air Force Avionics Laboratory, a variety of new phase‐processing techniques have been developed at the Charles Stark Draper Laboratory [1, 2, 3, 4]. Recently, special types of digital‐phase‐locked loops [3, 4]have been developed and appear to offer special advantages when applied to radio‐navigation receivers and timing receivers. One of these loops, which is referred to as aserial digital phase filter(SDPF), appears to be so simple in construction and useful in application as to be worth producing as a basic LSI building block.In this paper, the application of the SDPF to Omega receivers is explored. It is shown that the internal functions of an Omega receiver can be organized to take advantage of one or more SDPF's used in combination with an LSI microprocessor. The SDPF's can be used to reduce the load on the microprocessor by reducing the bandwidth of the phase data being presented to it. The SDPF's can also accomplish demodulation and analog‐to‐digital conversion, thereby eliminating the need for special circuitry to perform these functions. Because of the reduction in data bandwidth, there is an increase in efficiency and productivity of the microprocessor. The processing efficiency of the entire receiver is then more closely maximized with respect to hardware and software cost. The design approach is applicable to a bare‐bones receiver, which would incorporate the most elementary and inexpensive microprocessor or no microprocessor at all, or to a high‐performance airborne receiver where a variety of sophisticated functions must be performed automatically by the microprocessor.The paper is divided into five main sections. First, the organization of the receiver is described and the advantages of the recommended approach are pointed out. Then the SDPF is described in detail. Then the hardware developed for laboratory demonstration is described. The tracking performance of the receiver is discussed next, and theoretical and experimental data are provided for illustration. Finally, procedures for automatic synchronization are described and supported by experimental data. Some important areas, such as lane identification, propagation prediction, antenna design, etc., are treated only lightly as being more relevant to specific designs than to the problem of reducing cost by improving the efficiency of p

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb00721.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

ABSTRACTTheOmega navigation systemwill provide world‐wide position location information. As a result, Omega is being investigated as the information source for position location for several search and rescue (SAR) systems. One of these is the Global Rescue Alarm Net (GRAN). In order for Omega to fulfill the requirements of GRAN, the inherent lane ambiguity problem must be resolved. Presently anticipated ambiguity resolution techniques are not capable of resolving the nominally 72 nmi unambiguous lanes which result from the currently planned three Omega frequencies. In order for ambiguity resolution to be achieved, the addition of at least one frequency to the Omega format is being considered. This gives rise to the question of whether sufficient accuracy of position within an unambiguous lane can be obtained. This paper presents the results of the processing of experimental four frequency Omega data using the maximum likelihood estimato

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb00722.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

ABSTRACTA 6‐bit sensorprocessing method based on a digital, memory‐aided phase‐locked loop (MAPLL) and BCD rate multiplier clock synchronizing, provides building blocks for low‐cost Omega receivers. The method has been implemented in flight‐test hardware to provide raw Omega phase data suitable for direct interface with a microcomputer navigation processor. Experimental results and simulation studies of airborne systems will be presented.This work has been supported by NASA Langley Research Center Grant NGR 36‐009‐017 for application to low‐cost VLF methods for the general

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb00723.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

ABSTRACTpublished omega predicted propagation corrections(PPC's) are generally recognized as providing the most accurate means of correcting received OMEGA signals. However, computation of the published PPC's involves use of two sophisticated computer routines—one involving extensive propagation physics modeling, the other is a complex mathematical adjustment requiring online access to a large data base. Real‐time implementation of these routines in shipboard or airborne computers is not practical and thus, a number of algorithms have been developed in an attempt to obtain correction values which closely match published PPC's, yet impose a considerably less severe computer burden. In this paper, various of these algorithms—including functional approximations and simplified propagation physics models—are evaluated in terms of their accuracy relative to published PPC's and their relative computer burdens. The propagation models used in the PPC computation process are briefly examined in order to highlight areas of possible simplification for real‐time app

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb00724.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

ABSTRACTthis paper reports on a studywhich compared the expected cost and performance of Differential Omega with that of Loran‐C and VORTAC for general aviation area navigation. Analysis is directed toward a comparison of the systems with respect to specified performance parameters and the cost‐effectiveness of each system in relation to the specifications. Loran‐C offers the highest performance with respect to accuracy. Differential Omega requires the least expenditure. It was found cost ineffective to attempt to obtain complete coverage by expanding the existing VORTAC s

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb00725.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

ABSTRACTIntegrated omega/inertial navigation systemsappear attractive in airborne applications since the excellent short‐term accuracy of an inertial navigator is well‐complemented by the intermittent availability of bounded, moderately accurate OMEGA position fixes. There are a number of different approaches which can be taken to accomplish the desired system integration; three such approaches are considered. The first involves a straightforward output reset, the second is essentially a Kalman‐based variant of rate‐aiding and the third involves conventional optimal integration. These schemes are evaluated using models for various navigation system errors to yield predictions of system position and velocity error behavior. Additionally, the schemes are compared on the basis of operational factors such as ease of implementation and computer util

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1975.tb00726.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.tb00727.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY