Fundamentals of Satellite Navigation. GPS Systems Segments. GPS Satellite Signal Characteristics and Message Formats. Satellite Signal Acquisitions and Tracking. Effects of RF Interference on GPS Satellite Signal Receiver Tracking. Performance of Standalone GPS. Differential GPS. Integration of GPS with other Sensors. Galileo. The Russian GLONASS, Chinese Bediou, and Japanese QZSS Systems. GNSS Markets and Applications.

Understanding GPS : principles and applications

The Global Positioning System (GPS) is a satellite-based navigation and time transfer system developed by the U.S. Department of Defense. It serves marine, airborne, and terrestrial users, both military and civilian. Specifically, GPS includes the Standard Positioning Service (SPS) which provides civilian users with 100 meter accuracy, and it serves military users with the Precise Positioning Service (PPS) which provides 20-m accuracy. Both of these services are available worldwide with no requirement for a local reference station. In contrast, differential operation of GPS provides 2- to 10-m accuracy to users within 1000 km of a fixed GPS reference receiver. Finally, carrier phase comparisons can be used to provide centimeter accuracy to users within 10 km and potentially within 100 km of a reference receiver. This advanced tutorial will describe the GPS signals, the various measurements made by the GPS receivers, and estimate the achievable accuracies. It will not dwell on those aspects of GPS which are well known to those skilled in the radio communications art, such as spread-spectrum or code division multiple access. Rather, it will focus on topics which are more unique to radio navigation or GPS. These include code-carrier divergence, codeless tracking, carrier aiding, and narrow correlator spacing.

Global Positioning System: Signals, Measurements, and Performance

GPS satellite (4) ranging signals (6) received (32) on comm1, and DGPS auxiliary range correction signals and pseudolite carrier phase ambiguity resolution signals (8) from a fixed known earth base station (10) received (34) on comm2, at one of a plurality of vehicles/aircraft/automobiles (2) are computer processed (36) to continuously determine the one's kinematic tracking position on a pathway (14) with centimeter accuracy. That GPS-based position is communicated with selected other status information to each other one of the plurality of vehicles (2), to the one station (10), and/or to one of a plurality of control centers (16), and the one vehicle receives therefrom each of the others' status information and kinematic tracking position. Objects (22) are detected from all directions (300) by multiple supplemental mechanisms, e.g., video (54), radar/lidar (56), laser and optical scanners. Data and information are computer processed and analyzed (50,52,200,452) in neural networks (132, FIGS. 6-8) in the one vehicle to identify, rank, and evaluate collision hazards/objects, an expert operating response to which is determined in a fuzzy logic associative memory (484) which generates control signals which actuate a plurality of control systems of the one vehicle in a coordinated manner to maneuver it laterally and longitudinally to avoid each collision hazard, or, for motor vehicles, when a collision is unavoidable, to minimize injury or damage therefrom. The operator is warned by a heads up display and other modes and may override. An automotive auto-pilot mode is provided.

GPS vehicle collision avoidance warning and control system and method

System and method for preventing vehicle accidents in which GPS ranging signals relating to a host vehicle's position on a roadway on a surface of the earth are received on a first communication link from a network of satellites and DGPS auxiliary range correction signals for correcting propagation delay errors in the GPS ranging signals are received on a second communication link from a station or satellite. The host vehicle's position on a roadway on a surface of the earth is determined from the GPS, DGPS, and accurate map database signals with centimeter accuracy and communicated to other vehicles. The host vehicle receives position information from other vehicles and determines whether any other vehicle from which position information is received represents a collision threat to the host vehicle based on the position of the other vehicle relative to the roadway and the host vehicle. If so, a warning or vehicle control signal response to control the host vehicle's motion is generated to prevent a collision with the other vehicle.

Accident avoidance system

A location system is disclosed for wireless telecommunication infrastructures. The system is an end-to-end solution having one or more location systems for outputting requested locations of hand sets or mobile stations (MS) based on, e.g., AMPS, NAMPS, CDMA or TDMA communication standards, for processing both local mobile station location requests and more global mobile station location requests via, e.g., Internet communication between a distributed network of location systems. The system uses a plurality of mobile station locating technologies including those based on: (1) two-way TOA and TDOA; (2) home base stations and (3) distributed antenna provisioning. Further, the system can be modularly configured for use in location signaling environments ranging from urban, dense urban, suburban, rural, mountain to low traffic or isolated roadways. The system is useful for 911 emergency calls, tracking, routing, people and animal location including applications for confinement to and exclusion from certain areas.

Locating a mobile station and applications therefor

Disclosed herein is a system for rapidly resolving position with centimeter-level accuracy for a mobile or stationary receiver (4) This is achieved by estimating a set of parameters that are related to the integer cycle ambiguities which arise in tracking the carrier phase of satellite downlinks (5, 6) In the preferred embodiment, the technique involves a navigation receiver (4) simultaneously tracking transmissions (6) from Low Earth Orbit Satellites (LEOS) (2) together with transmissions (5) from GPS navigation satellites (1) The rapid change in the line-of-sight vectors from the receiver (4) to the LEO signal sources (2), due to the orbital motion of the LEOS, enables the resolution with integrity of the integer cycle ambiguities of the GPS signals (5) as well as parameters related to the integer cycle ambiguity on the LEOS signals (6) These parameters, once identified, enable real-time centimeter-level positioning of the receiver (4)

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A system using leo satellites for centimeter-level navigation

Attitude determination using GPS carrier phase has been applied successfully to aircraft in experiments by a number of researchers. In an effort to formally characterize its accuracy and bandwidth performance, a GPS attitude determination system was flight tested against an inertial navigation unit (INU). Based on completely separate physical principles, this testing provides an independent means of evaluating overall performance.

For the flight experiments, a twin-engine turboprop transport aircraft was outfitted with a specially designed attitude determination receiver. A strapdown ring laser gyro INU was operated in the main cabin as the independent reference. For system evaluation, a number of test maneuvers were executed, including pitch angles to ± 30 deg and bank angles to ± 60 deg. Performance in moderate turbulence was measured. The impact of structural flexure during aircraft maneuvering was evaluated.

Flight tests of attitude determination using gps compared against an inertial navigation unit.

A GPS attitude receiver for determining the attitude of a moving vehicle in conjunction with a first, a second, a third, and a fourth antenna mounted to the moving vehicle Each of the antennas receives a plurality of GPS signals that each include a carrier component For each of the carrier components of the received GPS signals there is an integer ambiguity associated with the first and fourth antennas, an integer ambiguity associated with second and fourth antennas, and an integer ambiguity associated with the third and fourth antennas The GPS attitude receiver measures phase values for the carrier components of the GPS signals received from each of the antennas at a plurality of measurement epochs during an initialization period and at a measurement epoch after the initialization period In response to the phase values measured at the measurement epochs during the initialization period, the GPS attitude receiver computes integer ambiguity resolution values representing resolution of the integer ambiguities Then, in response to the computed integer ambiguity resolution values and the phase value measured at the measurement epoch after the initialization period, it computes values defining the attitude of the moving vehicle at the measurement epoch after the initialization period

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System and method for generating attitude determinations using GPS

A GPS system that includes a GPS beacon (26) that receives a plurality of GPS signals (25), each having a carrier component and a pseudo-random code component, and generates in response thereto a plurality of beacon signals (27) having a carrier component phase locked to one of the carrier components and a pseudo-random code phase locked to one of the pseudo-random code components of the received GPS signals for transmission. A GPS receiver (32) receives the transmitted signals and makes Code Based Differential GPS position determinations by making range measurements for each of the pseudo-random code components of the GPS (25) and beacon (27) signals and in response computing values representing a position. Additionally, the GPS receiver can make Carrier Phase Differential GPS position determinations.

System and method for generating precise code based and carrier phase position determinations

A navigation system provides a significant level of protection against all forms of interference or jamming to GPS in a cost-effective way. The system employs a network of ground reference stations and Low Earth Orbiting (LEO) satellites in conjunction with GPS. A common-view ranging geometry to a GPS satellite is established that links a reference station and a user. A second common-view geometry to a LEO satellite between the same reference station and user pair is also established. The ground stations synthesize real-time aiding signals by making carrier phase measurements of GPS the LEO satellite signals. This aiding information is transmitted via the LEO satellites to the user receiver at high power to penetrate ambient jamming. The user receiver locks onto the carrier phase of the LEO satellite, demodulates the aiding information, then applies the carrier phase measurements and the aiding information to enable extended coherent measurements of the GPS signals. The system thereby recovers the GPS signals that would otherwise be lost to the jamming.

Clark E. Cohen

Papers

A system using leo satellites for centimeter-level navigation

Flight tests of attitude determination using gps compared against an inertial navigation unit.

System and method for generating attitude determinations using GPS

System and method for generating precise code based and carrier phase position determinations

Methods and apparatus for a navigation system with reduced susceptibility to interference and jamming