Showing papers on "GPS/INS published in 1989"

High-precision kinematic GPS differential positioning and integration of GPS with a ring laser strapdown inertial system

Abstract: Many fields, such as geodetic surveying, positioning of airborne sensors (photogrammetric cameras), laser bathymetry, airborne gravimetry, and hydrographic surveys, require accuracies in the decimeter or even centimeter range in differential positioning. Using the full potential of the GPS in a dynamic environment, the Institute of Astronomical and Physical Geodesy (IAPG) has carried out several kinematic tests with respect to land-based, shipborne, and airborne applications. After reviewing the main concepts in differential GPS kinematic positioning, this paper presents experiences with and practical results of kinematic GPS tests. Results of a Kalman filter covariance analysis are shown for the integration of GPS phase and pseudorange data with ring laser strapdown inertial systems in order to recover cycle slips and short-time loss of lock in GPS. In particular, the question is discussed of the extent to which inertial strapdown systems can be used to bridge these times and to maintain centimeter accuracy.

Cost‐Effective, High‐Accuracy Inertial Navigation

Abstract: In spite of the trend towards Global Positioning System (GPS)/ Inertial Navigation System Hybrids, certain applications demand a pure inertial solution to give high-accuracy navigation performance. Modern day Inertial Navigation Systems are dominated by the Ring Laser Gyro technology; however, these systems lie normally in the 1 nautical mile per hour class. To obtain a factor of improvement demands either: • Development of higher accuracy (and hence more expensive) inertial sensors; both gyro and accelerometer • Alternative mechanization of existing inertial sensors. An alternative mechanization which is ideally suited for today's ring laser gyros is one that can be borrowed from the past. This technique is the rate bias technique which solves many of the problems associated with dithered gyros, and in addition attenuates the effects of many of the inertial sensors (both gyro and accelerometer) errors. This paper discusses the design rationale and system design, which together with flight test results demonstrate that a rate bias ring laser gyro Inertial Navigation System provides a cost effective solution to the pure high-accuracy Inertial Navigation System requirement.

Integration of INS and GPS Measurements

Abstract: The paper describes the basic features of INS and GPS absolute and relative positioning. The conceptual system differences are compiled and positioning results are classified according to their error characteristics. System integration advantages in navigation, positioning, and gravity field determination are discussed.

GPS Navigation: Combining Pseudorange With Continuous Carrier Phase Using a Kalman Filter

Abstract: The notion of aiding GPS code-ranging information with the carrier-phase measurements has been around for quite some time, though little has been offered on it in the published literature. The integration of these two comple­mentary forms of data can provide highly precise position solutions cor­rupted by very little high-frequency error. This combination of data is particularly advantageous for high-dynamical situations. This paper presents two schemes that are based on the Kalman filter to integrate GPS code and carrier measurements efficiently. One of the schemes involves a general combination of the two types of measurements where the vehicle motion is described as a random process. In the other scheme, the continuous carrier phase measurements provide a dynamically exact reference trajectory in much the same manner as in an inertial system, and then the pseudorange data is used to update the reference trajectory via a Kalman filter. This method of integration looks especially attractive as a means of achieving good dynamical response while still retaining the bene­fits of filtering the pseudorange data. Simulated motion and real-life stationary receiver data were used to assess the characteristics of the filtering schemes under dynamical conditions. Issues involving cycle slips in the carrier phase, and their detection and correction are also discussed.

Data Processing for GPS/INS Integration

Abstract: This paper gives an overview of the data processing for the integration of GPS and INS. The role of the Kalman filter as the appropriate mathematical algorithms is described, and the basic variations in Kalman filter architecture are discussed.

Alternative Timing Networks with GPS

Abstract: : An approach to determining accurate time from GPS with an independent network of receiving stations has been investigated. The methods of using the Global Positioning System (GPS) for transferring time in previous work has been by the "common view" and "melting pot" methods. Both of these techniques have used simplified single frequency receivers operating on the clear/acquisition (C/A) GPS codes and assumes that the satellite transmissions are quality observables producing "GPS time", accurately traceable to UTC(USN0). In the case of "common view", the position of the satellite is assumed to be accurately known from the satellite transmissions. Then the time delays due to position at the two common view sites may be accurately measured for time comparisons. In the "melting pot" method, an individual site measures "GPS Time" as determined from observing all GPS satellites in view resulting in an accurate over-solution of the GPS system time. The satellite broadcasts then provide the UTC - GPS time correction. The investigation into an independent network was performed on the basis of using the simplified CIA receiving equipment to produce accurate timing information regardless of the GPS broadcast information accuracy. The technique can be used to improve the inherent capabilities of these single frequency receivers or maintain accuracy with degraded GPS signals. The similarities with geodetic positioning using GPS will be described. A proof-of-concept experiment will be discussed and data presented to verify the technique.