摘要:

ABSTRACTin a recent series of experiments, the General Electric Corporate Research and Development Center demonstrated effective continental land mobile communications and automatic real—time vehicle position fixing. A station wagon was equipped with a specially designed antenna, a slightly modified commercial VHF transceiver, and a digital tone—code communications bandwidth ranging responder. The General Electric Radio— Optical Observatory near Schenectady, NY served as the major earth terminal; a commercial VHF base station with a satellite antenna deployed first in Washington, DC and later in Tucson, AZ, represented a local control ground station. Communications were relayed by NASA's ATS—3 geosynchronous satellite; both ATS—1 and ATS—3 were used for position fixing the vehicle.During the six week test schedule across the continental United States, real—time vehicle positions on the order of one quarter mile were achieved. Post experiment data processing yielded vehicle position fixing accuracy on the order of a few hundred feet, under most circumstances. Simultaneous ranging measurements to the local control (ground truth reference) base station provided a measure from which to estimate ionospheric propagation time delays between the vehicle and the satellite. The single test which showed position fixing inaccuracy on the order of one half mile occurred during an ionospheric disturbance; the disagreement in true and measured vehicle positions suggests an ionospheric gradient between the vehicle and the fixed station of approximately 2 × 1017electrons/m2, over the separation distance of 350 miles. Using a simple model to predict the VHF ionospheric propagation time delay would have resulted in vehicle positions accurate to within one half mile. Future satellite ranging operations at frequencies above 800 MHz would not be affected by propagation delays in the ionosphere.Although the experiments were conducted with an automobile, the technology is most certainly applicable in the maritime and aeronautical arena. Indeed, it is only in the land mobile environment that accurate true vehicle positions can be determined for verifying position fixing accuracy. All measured vehicle positions were compared with true vehicle positions as plotted on U.S. Geological Survey topo

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb02257.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTThe united states coast guardhas performed a successful demonstration on the St. Marys River of the feasibility of precision navigation in restricted waterways using Loran–C as a prime sensor.The St. Marys River, located in northern Michigan near the city of Sault Ste. Marie, serves as the only water shipping route connecting Lake Superior with the rest of the Great Lakes and the St. Lawrence Seaway. The 65–mile river, which is traversed by iron ore carriers up to 1000 feet long and 105 feet wide, has channels as narrow as 300 feet. A special four–station Loran–C mini–chain was established by the Coast Guard in 1976 to provide an all–weather, year–round navigation capability. Initial tests were performed on USCG vessels to determine the feasibility of using Loran–C as a navigation aid on the St. Marys River. The navigation accuracy objective was a maximum cross–track error on the order of 25 feet using Loran–C data integrated with gyrocompass heading information.This paper describes the operational environment, Loran–C mini–chain, shipboard user equipment configuration and software approach, and results of the feasibility tests. Various statistical performance parameters are presented on the Loran–C signals, static accuracies, and dynamic navigation performance.The results of the USCG feasibility tests to‐date indicate that Loran‐C offers great promise

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb02258.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTConceived as a bridge betweenthe VHF/UHF ILS and the future international standard Microwave Landing System, ISMLS provides all the operational benefits of conventional ILS with few of the technical headaches.Several ISMLS installations are presently commissioned for public use serving in some cases at sites where site preparation costs for conventional ILS would have exceeded by far the total cost of the rest of the ISMLS installations in commission. These facilities are the world's first public‐use microwave landing systems.This paper describes the ISMLS, its signal format, how it copes with difficult siting problems and how it manages to bridge the gap between the existing VHF/UHF system and the future worldwide system, serving the immediate needs of the aviation communit

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb02259.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb02260.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTTheDodNavstar global positioningSystem (GPS), expected to be implemented by the mid–1980's, is designed to provide a highly accurate, three dimensional, worldwide navigation capability. The FAA has been investigating its use with other resources for potential ATC applications in which surveillance and data communications, in addition to navigation, are provided. Utilization of the GPS, either unmodified or modified, to support future ATC requirements, is of considerable interest because of the potential economic advantages associated with the joint use of satellites.This paper describes several concepts that have been investigated, for possible CONUS ATC applications, together with some of their significant features. These include user, space and ground segment configurations, spectrum requirements, and surveillance capacity. For the latter, two specific aircraft accessing schemes are considered—polling and time division multiple access (TDMA). The results indicate a high technical potential for providing the surveillance, navigation and data communications functions, but economic tradeoffs must still be examined in terms of user equipment complexity and overall system costs.This paper is based upon satellite system studies performed at MITRE/METREK for the FAA's Office of Systems Engineering Management, under Contract No. DOT FA70WA–2448. The information presented does not necessarily reflect the official views or policy of th

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb02261.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb02262.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb02263.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb02264.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb02265.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1978.tb02266.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY