Showing papers on "GNSS augmentation published in 1997"

Method and system for a differential global navigation satellite system aircraft landing ground station

Abstract: A differential GNSS ground station is disclosed which generates and broadcasts highly veracious GNSS satellite differential correction data suitable for use in the landing of aircraft. In this context, "veracious` includes the qualities of both accuracy and integrity wherein the broadcast differential correction data is corrupted by a lower level of errors than is customary for the current state of the art and the broadcast differential correction data includes reliable estimates of the noise errors and bias errors corrupting the differential corrections for each GNSS satellite signal. The ground station comprises at least two independent GNSS satellite signal receivers, a processing apparatus for collecting and processing information from the at least two independent GNSS receivers, and a transmitter for broadcasting the composite DGNSS correction signals over a distance.

Ionosphere tomography with data from satellite reception of Global Navigation Satellite System signals and ground reception of Navy Navigation Satellite System signals

Abstract: GPS/MET, a multichannel Global Positioning System (GPS) receiver onboard the small research satellite MicroLab 1, is the first example of a research tool of great importance for ionospheric research. In the near future, other satellites with GPS/GLONASS (Global Navigation Satellite System (also GNSS)) receivers will be launched. Their main purpose is lower atmosphere research, but because of the necessity to correct for plasma influences, “ionospheric” data will be available as a side product. The occultation of GNSS signals offers the possibility to gain very good quality height profiles of electron density by means of classical inversion techniques. The profiles are averaged horizontally. This paper concentrates on the possibility to complement inversion results with electron content data gained on the ground using beacon signals of low orbiting satellites (e.g., the U.S. Navy Navigation Satellite System (NNSS)). The data combination offers several possibilities for ionospheric tomography. Several GNSS scanning satellite scenarios are assessed, and their ionospheric imaging/tomography merits are discussed. An example result for the inversion of GPS/MET data is shown. The results of simulations with model ionosphere data are used to demonstrate tomographic reconstruction techniques based on the combination of “space” and “ground” electron content. The simulation results have direct applicability to observed data.

Description of the FAA's Local Area Augmentation System (LAAS)*

Abstract: The Local Area Augmentation System (LAAS) is the Federal Aviation Administration's ground-based augmentation system (GBAS) for local area differential GPS (DGPS). It will support all categories of precision approach. LAAS is currently under advanced development and specification. The purpose of this paper is to provide a system description of LAAS and to describe important related developments for the aviation and navigation communities. Both top-level and intermediate-level descriptions are given, with emphasis on the Ground Segment. Three distinguishing advances are described in more detail: Multipath Limiting Antenna, Airport Pseudolite, and a method for transforming integrity parameters from the pseudorange to the position domain.

GNSS local constellation/acquisition aiding system

Abstract: An apparatus and method are disclosed of providing position indicating signals to a GNSS receiver in an area of poor reception of satellite signals from the GNSS or when a dedicated system under local control is required. The method includes the steps of disposing a plurality of stationary transceivers proximate the area of poor reception and calculating a global position of each stationary transceiver based upon information contained within signals received from at least some satellites of the GNSS. The method further includes the steps of transmitting a local global positioning signal from each of the stationary transceivers to the GNSS receiver in the area of poor reception, such local global positioning signals including at least the global position of the transmitting stationary transceiver.

Integration of aime augmentation into GNSS products

Abstract: A global navigation satellite system (GNSS) receiver for use in an aircraft is disclosed. The GNSS receiver includes receiver circuitry for receiving satellite signals containing satellite data from a multiple GNSS satellites. The receiver circuitry generates a first navigation solution for the aircraft as function of the satellite data. A first GNSS receiver output couples to an inertial reference system (IRS) and provides the satellite data to the IRS. The IRS generates a second navigation solution for the aircraft as a function of the satellite data and as a function of IRS position data. A first GNSS receiver input couples to the IRS and receives the second navigation solution from the IRS. The GNSS receiver provides at a second output aircraft position information as a function of the second navigation solution.

Real time differential GPS and GLONASS vehicle positioning in urban areas

Abstract: This paper describes a research programme carried out by the Institute of Satellite Navigation (ISN) and Racal Survey Ltd. to examine the performance of differential positioning using both the GPS and GLONASS satellite systems for vehicle positioning. The work involved developing a differential GNSS positioning system for a vehicle using GNSS receivers developed by the ISN and Ashtech and using Racal’s LandStar regional differential system. The programme has involved extensive real time vehicle positioning trials in urban areas. Two aspects of vehicle positioning performance have been concentrated on, (i) fix density, and (ii) positioning accuracy. The results show that combining GPS and GLONASS significantly improves both stand alone and differential positioning accuracy compared to using just GPS alone. The results also show that combined GNSS supports a greater differential correction age without the same accuracy degradation that GPS exhibits. This, in turn, increases the GNSS fix density. Even with the same correction age, GNSS has a better fix density by about 10%. This increase in fix density will allow improved vehicle positioning in an in-car navigation system with a lower level of augmentation. In summary, these results have shown that GNSS has significant advantages over GPS as the satellite positioning component of a vehicle positioning system.

Fault tolerance of the Global Navigation Satellite System using system-level diagnosis

Abstract: The Global Navigation Satellite System (GNSS) is a space-based positioning system that can track aircraft, to within a few feet, anywhere in the United States of America. With augmentations based in other countries, the GNSS becomes a truly global positioning system, able to track aircraft anywhere on the globe with accuracies on the order of a few feet. We investigate the application of system-level diagnosis (SLD) to the GNSS to assess the diagnosability and fault tolerance of the system. We show, in a deterministic manner the number of faulty elements that can exist in the system and still allow for the accurate diagnosis of the system. Our deterministic approach is in contrast to other known probabilistic approach.

Global Navigation Satellite Systems

Abstract: GPS (and its Russian analogue, GLONASS) are reviewed. Conceived a quarter of a century ago, it represents the most significant step forward in radionavigation. Its deployment was relatively slow. The explosive growth of low cost civil receivers has only appeared in the last five years or so, and the relationship between the US military authorities, who own and operate GPS, and the civil international community, is slow in developing a mutually acceptable position. A review of GPS against the required navigation performance criteria leads to the requirements for augmenting GPS into GNSS-1-in particular WAAS by the FAA, EGNOS by the European tripartite group, and MSAS in Japan. A description of these augmentation systems, based on navigation payloads on board geostationary satellites, is given, with particular reference to Inmarsat. Associated institutional issues are discussed briefly as well as an interactive synthesis of candidate designs for GNSS-2.