Showing papers on "GPS/INS published in 1983"

GPS Navigation Using Three Satellites and a Precise Clock

Abstract: Navigation using GPS generally requires that the user track four satellites to resolve his 3-D spatial position and time bias. There are several reasons why it is desirable to navigate while tracking only three satellites: —The proposed 18 satellite GPS constellation will exhibit substantial periods of poor four satellite geometry over large geographic areas several times a day. —Failure of a GPS satellite in orbit will result in periods of only three-satellite availability over large geographic areas. —During establishment of the operational GPS constellation, there will be long periods of three-satellite GPS coverage. Three-satellite GPS navigation can be accomplished by equipping the user with a precise clock. The required stability of the clock is a function of the maximum allowable PDOP (Position Dilution of Precision) and the time interval between updates of the clock. Clock updates can be accomplished by tracking four GPS satellites, tracking one GPS satellite from a known location, or conventional time transfer methods. This paper presents a formula for computing PDOP and its components, HDOP (Horizontal DOP) and VDOP (Vertical DOP), as a function of three-satellite geometry and clock stability. This formula is used to plot HDOP and VDOP versus time for representative high quality quartz crystal and low-cost rubidium clocks for two scenarios of satellite geometry. The stability and environmental sensitivity of high quality quartz crystal and low-cost rubidium clocks are discussed.

Multiconfiguration Kalman filter design for high-performance GPS navigation

Abstract: This paper describes the design, implementation, and performance of a real-time multiconfiguration Kalman filter for high-performance Navstar global positioning system (GPS) navigation. The design provides extreme flexibility in order to operate with a wide variety of host sensors. It configures automatically (four filter configurations) based upon the host vehicle requirements and sensor availability, in order to process GPS measurements and provide the best estimate of the navigation states. Two new techniques, namely an unaided dead-reckoning Kalman filter implementation and an automatic inertial platform tilt estimation control scheme, are developed to improve the navigation accuracy, especially for high-dynamics applications. Performance results are presented to demonstrate the advantages of these techniques.

A Kalman Filter Approach to Precision GPS Geodesy

Abstract: The high stability of the GPS signals makes it possible to determine differential position over short baselines with an accuracy of the order of centimeters. This has been demonstrated using very long baseline interferometry (VLBI) methods of radio astronomy. This paper presents an alternative approach using Kalman filter methods. It is based on an adaptive filter concept developed by D. T. Magi11 in 1965. The scheme employs parallel Kalman filters with each filter being modeled for a different integer wavelength assumption. As the phase measurement sequence progresses, the adaptive scheme “learns” which Kalman filter corresponds to the correct hypothesis, and thus it both resolves the wavelength ambiguity and estimates differential position simultaneously. Simulated results are presented which indicate convergence in about 10 minutes of satellite observation time.

Sensitivity Analysis of an Integrated NAVSTAR GPS/INS Navigation System to Component Failure

Abstract: This paper examines the performance of an integrated GPS/INS navigation system with respect to component failures. The paper is divided into three sections. The first section details the system configuration by which the navigation components are integrated. The second section examines the modelling methods used to simulate each of the components and the third section analyzes the simulation results. Four modes of component failure are investigated. They are GPS outage, baro-altimeter failure, inertial failure and satellite obscuration.

An integrated multisensor aircraft track recovery system for remote sensing

Abstract: This paper describes an application of the Kalman filter in a track recovery system (TRS) for postflight processing of aircraft navigation sensor data. The track recovery system has been successfully used as a key component of the Canadian aerial hydrography pilot project for mapping of shallow coastal waters. Recorded data from an inertial navigation system (INS) is combined with data obtained from a number of auxiliary sensors to construct a set of error measurements. The measurements are prefiltered to compress the data and are then processed using a U-D factorized Kalman filter and a modified Bryson-Frazier smoother to produce estimates of the time-correlated sensor errors. The flight profile is obtained by subtracting the computed error estimates from the recorded INS data. The residual errors observed in processing real data collected in a number of field tests are less than 1 m in position and less than 0.03 degrees in attitude.