摘要:

ABSTRACTThis experiment demonstrated the obtainable accuracy for estimating changes in a receiver antenna position using Doppler techniques and the NAVSTAR Global Positioning System (GPS). The antenna was periodically moved to three locations approximately 2 to 3 meters apart. The moves occurred within a one minute Doppler count interval every fifteenth interval until at least six Doppler measurements were made for each location change. These measurements were used to determine the observed change in range from the antenna to the GPS satellite due only to the movement of the antenna. The calculated change in range was computed from the surveyed distance moved and the angular differences in elevation and azimuth between the direction of the move and the direction of the satellite. The observed and calculated changes in range were compared. The three‐dimensional antenna position changes were estimated using six observed change in range measurements for each location change. The estimated results were compared with surveyed values and demonstrated subdecimeter accurac

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01449.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTThe Defense Mapping Agency in conjunction with other government agencies is sponsoring the Development of GPS user equipment which will benefit greatly the Mapping, Charting and Geodesy community. The developments include the firstGPSreceivers for space applications and GPS receivers for geodetic survery applications. Both projects utilize technical support of the Naval Surface Weapons Center at Dahlgren.The receiver for space applications (GPSPAC) is a joint program funded by DMA and NASA for the development of GPS receiver hardware to fly as part of NASA's LANDSAT Program. The real‐time acquisition of precise ephemeris information will greatly enhance the utility of the imagery acquired by this satellite to the users, and will serve as a pilot experiment for future application of GPS mapping the earth from space. The GPS geodetic receiver development, which will provide prototype receivers for utilization in terrestrial surveying operations, has the potential to significantly enhance the accuracy of point geodetic surveys over the current TRANSIT user hardware capability. The improved accuracy will come with a corresponding reduction in time required to occupy the site and therefore offers operational cost reductions. This program is jointly sponsored by DMA, NASA, USGS and NOAA/NGS. The project engineering work on this program is being carried out at NSW

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01450.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTRecent advancements in electronics technology, such as Very High Speed Integrated Circuits (VHSIC) and Very Large Scale Integration (VLSI), have made the use of embedded microprocessors not only feasible, but the most economical approach to designing modern airborne navigation systems. The integration of GPS and JTIDS with existing navigation systems naturally leads to the use of multiple embedded microprocessors. To effectively use multiple processors, a design procedure must be developed to allocate navigation tasks among processors.Procedures exist for evaluating the performance of computer networks once tasks have been allocated. In particular, simulations can be used to determine loadings and identify bottlenecks. However, these methods cannot be applied until considerable detailed design work has been completed. This paper addresses an approach to allocating navigation tasks early in the design process.The methods discussed are based on applying rate‐distortion techniques from communication theory to navigation system design. All navigation activities are broken down into elementary functions. Rate‐distortion methods are used to assess the impact on rms position and velocity errors of limiting communication bandwidths among elementary functions. Groups of functions that require high‐bandwidth communication are assigned to the same microprocessor, while those that can perform effectively with lower‐bandwidth links are separated. This approach also allows the trade‐offs in function groupings to be quantified so that decisions regarding the use of VHSIC and VLSI can be based on quantitative assessments of

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01451.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTFour algorithms for computing the attitude matrix in a strapdown navigation system are described. The algorithms studied are Bortz 9‐direction cosine, Bortz‐quaternion, Lie algebra and Cayley transform.Each algorithm has a fast cycle and a slow cycle. In the fast cycle short term attitude information is computed in a three parameter array. This information is then used to compute the attitude matrix in the slow cycle and the 3 parameter array is reinitialized at the start of the slow cycle. In the Bortz‐quaternion and Lie algebra quaternion algorithms, the attitude information is resident in the quaternion and the attitude matrix then computed from the quaternion, whereas in the Bortz 9‐direction and Cayley transform algorithms, the attitude matrix is directly updated. The attitude matrix computed from the Bortz 9‐direction cosine algorithm is orthonormalized in a separate routine, whereas the Bortz quaternion and Lie algebra quaternion algorithms provide an orthogonal matrix which is normalized by dividing by the length of the quaternion. The attitude matrix computed from the Cayley transform algorithm is inherently orthonormal. The overall computer efficiency is c

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01452.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTThe task of communicating with a satellite from a fixed or moving station on or near the earth is becoming one that must be accomplished in an increasing number of applications. It is frequently necessary in these applications to point an antenna at the satellite, and to know the range and/or range‐rate along the line‐of‐sight connecting station and satellite, within some allowable tolerance, in order to lock on and communicate successfully. Errors in the navigation variables of the station, that is, its three‐dimensional position and velocity, and in the knowledge of position and velocity of the satellite, contribute to errors in “lockon” variables, i.e., antenna‐positioning, range, and range‐rate. This paper summarizes the formulas that allow the errors in lockon variables to be calculated, given the errors in satellite and station navigation variables. The error sensitivities, that is, the partial derivatives of the errors in lockon variables as functions of errors in navigation variables, are presented

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01453.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTMatthew Fontaine Maury, Officer in Charge of the Depot of Charts and Instruments (later the U.S. Naval Observatory and Hydrographical Office) developed a system of charts for the oceans of the world. Information for the compilation of the charts was furnished by the individuals who would benefit from the publication of the combined experiences of the maritime community. Data on various environmental forces that directly affected the safe and timely navigation of ships on long ocean voyages were incorporated into the charts. Information carried on the charts included tracks most frequently sailed, average time for sailing, wind direction and frequency, trade wind data, sea surface temperature, rain and storm data, and, for the whaling industry, information relating to the likelihood of locating whales in the various oceans. Between 1847 and 1860, when the last chart in the series was published, Maury had succeeded in developing a navigation system based on the scientific application of data furnished by the U.S. Navy, Merchant Marine, and international observers.

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01454.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTThe microwave landing system represents a major advancement in accurate, highly flexible positioning systems permitting the precise definition of curved approach paths. However, the exploitation of these capabilities also requires a comparable advancement in the presentation of information to the pilot. This paper presents a simulator investigation of various prediction and quickening algorithms in computer generated forward‐looking displays to improve manual aircraft control on curved MLS approaches. Results indicate that second‐ and third‐order predictor displays provide the best lateral performance. Intermediate levels of prediction and quickening provide best vertical control. Prediction/quickening algorithms of increasing computational order significantly reduce aileron, rudder, and elevator control responses, reflecting successive reductions in cockpit workload. Whereas conventional crosspointer displays are not adequate for manual control during curved landing approaches, perspective displays with predictors and some quickening in the vertical dimension only are highly effective. Additional research is needed to optimize the display for vertical co

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01455.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTA system is described which relates to the FAA's developmental Discrete Address Beacon System (DABS). However, the DABNLS is an integrated system and would provide not only air traffic control surveillance data and a two‐way data link (including ground derived traffic advisories) of DABS, but it would also provide precision area navigation and versatile landing guidance with a full Category IIIc capability. Further, its transmissions include three‐dimensional position data on all aircraft, thus supplying simple straight forward means for a cockpit traffic environment display on an effective and economic collision avoidance system with horizontal as well as vertical escape maneuver capabilities.For the enroute structure the DABNLS would utilize a single pair of L‐band frequencies for the discretely addressed up‐link interrogations and down‐link replies. The ground facility would make precise azimuth and range measurements on the bi‐phase coded reply pulses, and, with the reported altitude data, digitally process the data to obtain the aircraft's latitude/longitude and other parameters. This data is broadcast on the following interrogation for navigation by the addressed aircraft, and for collision avoidance purposes by all other aircraft. The ground facility uses the data for ATC purposes. Multiple channels would be used in the terminal areas, each with the addition of elevation facilities for landing guidance.Substantial economies would be accrued with both ground and airborne equipment, as well as added operational capabilities, with implementation of DABNLS. Even a single channel airborne transponder would provide ATC surveillance, area navigation, and collision avoidance for the smallest aircraft throughout the country, and make practical for the first time the longstanding FAA desire of surveillance of a

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1981.tb01456.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.tb01457.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY