摘要:

ABSTRACTThis paper describes the revisions recently made to the Radio Technical Commission for Maritime Services Special Committee‐104 (RTCM SC‐104) standard on differential Global Navigation Satellite System (GNSS) broadcasts. A major contribution of the new RTCM standard is to introduce several new messages that support differential GLONASS operations. Specifically, new GLONASS messages are provided: (1) differential corrections, (2) reference station coordinates, (3) satellite constellation health data, (4) radiobeacon almanac, (5) null message, and (6) ASCII text that accommodates languages other than English.Other messages are defined as well. An important new message indicates the datum employed by the reference station, if it uses a datum other than WGS‐84 (GPS) or PZ‐90 (GLONASS). A second new message provides time, so that users logging data can identify the day of the week and determine UTC time. Another provides the GPS/GLONASS offset, in order to support combined GPS/GLONASS operation. A fourth new message supports higher precision in the reference station antenna phase center location.In addition to the new messages, new material is included that provides additional guidance to users of differential GNSS services. The major issues are discussed in thi

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1996.tb01926.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe objective of this research is to demonstrate that an indoor sensing system consisting of pseudo‐satellites (pseudolites) and modified commercial GPS receivers can be used to sense and control the relative position and attitude of prototype robotic space vehicles in a laboratory environment. The long‐term goal for this research is to develop technologies that will enable robotic vehicles to perform complex maneuvers such as autonomous navigation, rendezvous, multivehicle formation flying, and assembly in space. An experimental hardware system consisting of a prototype space robot, target vehicle, and GPS system has been devised to closely emulate real space systems. Since the experiments take place indoors where GPS satellite signals cannot be received, several GPS pseudolite transmitters have been built and installed around the perimeter of the laboratory to provide the GPS signals. The indoor GPS environment created by the close‐range pseudolite transmitters required development of new algorithms for resolving vehicle positions and attitudes from the carrier‐phase measurements. Therefore, the most novel aspect of this research has been the development of GPS for indoor sensing, where it has the potential to be applied to indoor mobile robots and to automated manufacturing systems. This paper presents the theoretical formulation and experimental results of the use of this indoor GPS system for performing rendezvous between a prototype space robot vehicle and a passive target

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1996.tb01927.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTMultipath is potentially the largest contributor to positioning error for differential GPS. Airborne receivers will be subject to multipath from the airframe and from the ground and other objects during precision approach. Extensive flight testing of GPS receiver systems on the new Boeing 777 has been performed. One of the characteristics of this new aircraft is its large wingspan, which may cause significant GPS multipath positioning errors. Experiments were carried out to quantify these effects under various flight regimes. The 777 flight test experimental set‐up involved both narrow‐ and standard‐correlator receivers. The data were analyzed with particular attention to assessing the multipath effects during precision approach. Flight testing of GPS receivers on the 747–400 and 737 has also been performed, and the data analyzed to assess the level of airframe multipath. This paper compares the apparent airframe multipath effects for the two commercial transport airframes—the 747–400

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1996.tb01928.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTA prototype autonomous surface craft (ASC) has been developed at the MIT Sea Grant College Program's Autonomous Vehicles Laboratory to collect bathymetric data in littoral regions economically. Potential uses of this data include coastal surveys and monitoring, mine countermeasure operations, and physical and biological oceanography. This paper describes the ASC and presents field experiment results.For bathymetric data to be of value, the precise location of each data point must be known. To accomplish this, the ASC uses a differentially corrected GPS‐based fuzzy guidance controller to track to and cross a series of transect‐defining way‐points. The fuzzy controller is programmed in C and downloaded to a small on‐board computer for execution. The fuzzy controller was found to be relatively easy to develop (not requiring a complex mathematical model of the vehicle's dynamics), simple to tune, and robust to external disturbances. Field test results are presented and show that the guidance controller performed well on comple

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1996.tb01929.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe project Integrity of Satellite Navigation (ISAN) investigates the potential of GNSS (GPS and/or GLONASS) as part of a hybrid GNSS Landing System (GLS) for precision approach and landing down to Category (CAT) III. Specifically, accuracy, integrity, continuity of function, and availability are considered. The accuracy and continuity of function of the GLS were demonstrated in more than 400 flight tests in a commuter aircraft, and landing trials with a Boeing 757 aircraft during the Boeing Autoland Program. These flight tests demonstrated that the navigation system provides sufficient accuracy to perform landings according to suggested FAA requirements of CAT I to III.The present objectives of ISAN are the analysis and improvement of the system availability and establishment of a method to approve system integrity standards. A combination of GPS/GLONASS is considered for the GLS availability improvement. For reasons of integrity monitoring, satellite anomalies, atmospheric effects, and multipath problems on the signal‐in‐space, as well as GPS receiver failures, are taken into account in a GLS Closed Loop Simulation Test Bed installation, including a GPS Simulator to validate the system integrity in defined test scenar

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1996.tb01930.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThis paper investigates the use of GPS to assist with the marking and reporting of lanes cleared of mines in preparation for a military amphibious assault. The feasibility of using GPS, inertial navigation systems (INS), GPS/INS, GPS translators, radar, laser, and videometric technologies is included in the concept study. Sensor data from the mentioned devices have potential for enhancing overall system performance and/or mission success during shallow‐water mine countermeasure operations. The main objective of the study is to assess the advantages and disadvantages of the various sensor technologies as regards cost, accuracy, ruggedness, size, weight, power, and other considerations. With regard to GPS, dynamic robustness and vulnerability aspects are reviewed. Both differential and absolute GPS positioning accuracy are discussed for present and future systems within the constraints of the amphibious application. A discussion of the background for the study and the assumed scenario and environment for the operation is presented. Recommendations and conclusions are give

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1996.tb01931.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTCoastal radio beacon stations are now widely used to transmit corrections for differential satellite navigation systems (DSNS). The paper describes a computer model developed for predicting the stations' coverage areas: the regions in which all the key parameters of the signal, field strength, signal‐to‐noise ratio, and signal‐to‐interference ratio meet the minimum values specified for an internationally acceptable service. Each parameter is examined, and the factors that control it are elucidated. Groundwave and skywave field strengths of signals and atmospheric noise intensity are derived from International Telecommunication Union (ITU) data. The fading of the radio beacon signal at night as a result of skywave propagation is taken into account. The model also predicts the levels of interference from cochannel and adjacent‐channel beacons received via groundwave and skywave propagation, which commonly limits coverage in Europe. The paper presents coverage prediction diagrams for Europe and the Middle East produced using

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1996.tb01932.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTIn a previous paper, an approach to celestial navigation is presented that allows a vessel's latitude, longitude, course, and speed to be estimated simultaneously. The development in that paper assumes that the vessel is sailing a rhumb‐line track at a constant speed. In this paper, the approach is extended to cover the case where observations are taken over several legs of a voyage. A single least‐squares solution for all sailing parameters is developed. The algorithm presented in this paper is not limited to celestial navigation, but is applicable to any situation in which observations over several legs of a voyage are to be combined in a single solut

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1996.tb01933.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY