scispace - formally typeset
Search or ask a question

Showing papers on "GPS/INS published in 1993"


Patent
28 May 1993
TL;DR: In this paper, a combined GPS and dead-reckoning (DR) navigation sensor for a vehicle is presented, in which a pair of modifications are made to an otherwise conventional Kalman filter.
Abstract: An embodiment of the present invention is a combined GPS and dead-reckoning (DR) navigation sensor for a vehicle in which a pair of modifications are made to an otherwise conventional Kalman filter. Process noise is adapted to cope with scale factor errors associated with odometer and turning rate sensors, and correlated measurement error processing is added. When only two Doppler measurements (PRRs), or three with an awkward three-satellite geometry, are available, DR error growth can nevertheless be controlled. The measurement error correlations in the conventional Kalman filter covariance propagation and update equations are explicitly accounted for. Errors induced by selective availability periods are minimized by these two modifications.

340 citations


Journal Article
TL;DR: In this article, a general model for the georeferencing of remotely sensed data by an onboard positioning and orientation system is presented as a problem of rigid body motion, and the determination of the six independent parameters of motion by discrete measurements from inertial and satellite systems is directly related to the problem of exterior orientation.
Abstract: A general model for the georeferencing of remotely sensed data by an onboard positioning and orientation system is presented as a problem of rigid body motion. The determination of the six independent parameters of motion by discrete measurements from inertial and satellite systems is directly related to the problem of exterior orientation. The contribution of each measuring system to the determination of the three translational and three rotational parameters is treated in detail, with emphasis on the contribution of inertial navigation systems (INS) and single- and multi-antenna receivers of the Global Positioning System (GPS). The advantages of an integrated INS/GPS approach are briefly discussed

160 citations


Patent
19 Mar 1993
TL;DR: In this paper, the authors present a system for pointing a directional antenna using two GPS antennas mounted at horizontally opposed extremities of the directional antenna, the placement is such that the GPS antennas lie on a line having a normal vector approximately parallel to a boresight.
Abstract: An embodiment of the present invention is a system for automatically pointing a directional antenna. The system comprises two GPS antennas mounted at horizontally opposed extremities of the directional antenna, the placement is such that the GPS antennas lie on a line having a normal vector approximately parallel to a boresight of the directional antenna. The outputs from the GPS antennas are downconverted to a measurement frequency and differentially phase compared for each of a plurality of radio visible GPS satellites. A measurement controller that receives the phase comparisons. A navigation computer receives measurements from the measurement controller and uses a microprocessor to calculate the GPS latitude and longitude and the attitude angles of the pair of GPS antennas. A servo points the directional antenna at a particular target communications satellite, based on the computed azimuth, elevation, latitude, and longitude, as provided by the navigation computer. One of these servos is used to move the GPS antennas in roughly a circle to average out multipath effects to improve accuracy and to reduce integer ambiguities.

136 citations


Patent
29 Mar 1993
TL;DR: In this paper, a device for determining the position of a vehicle comprises a GPS (Global Positioning System) receiver which supplies vehicle position data at regular intervals on the basis of data received from satellites, a device (1) for dead-reckoning on basis of the position data from the GPS receiver, a compass (2) and at least one wheel sensor (3), and a correction unit (4) which corrects the deadreckoning values supplied by the device in dependence on comparison with road position coordinates read from a mass memory (5), notably with characteristic road position
Abstract: A device for determining the position of a vehicle comprises a GPS (Global Positioning System) receiver (6) which supplies vehicle position data at regular intervals on the basis of data received from satellites, a device (1) for dead-reckoning on the basis of the position data from the GPS receiver (6), a compass (2) and at least one wheel sensor (3), and a correction unit (4) which corrects the dead-reckoning values supplied at regular intervals by the dead-reckoning device (1) in dependence on comparison with road position coordinates read from a mass memory (5), notably with characteristic road position coordinates, and outputs the corrected values as vehicle position coordinates. For autonomous correction of the data from the GPS receiver the vehicle position coordinates supplied by the correction unit (4) are applied to the GPS receiver (6), the position data derived from the satellite reception in the GPS receiver (6) being corrected in conformity with the vehicle position coordinates supplied by the correction unit (4) and being applied in corrected form to the dead-reckoning device (1 ) as position data.

103 citations


Proceedings ArticleDOI
26 Jul 1993
TL;DR: The results show that with careful and detailed modeling of error sources, low cost inertial sensing systems can provide valuable position information.
Abstract: A low-cost, solid-state inertial navigation system for robotics applications is described. Error models for the inertial sensors are generated and included in an extended Kalman filter (EKF) for estimating the position and orientation of a moving robot vehicle. A solid-state gyroscope and an accelerometer have been evaluated. Without error compensation, the error in orientation is between 5-15/spl deg//min but can be improved at least by a factor of five if an adequate error model is supplied. Similar error models have been developed for each axis of a solid-state triaxial accelerometer. Linear position estimation with accelerometers and tilt sensors is more susceptible to errors due to the double integration process involved in estimating position. WIth the system described here, the position drift rate is 1-8 cm/s, depending on the frequency of acceleration changes. The results show that with careful and detailed modeling of error sources, low cost inertial sensing systems can provide valuable position information.

91 citations


Journal ArticleDOI
TL;DR: In this paper, an experiment is described to validate the concept of developing an autonomous integrated spacecraft navigation system using onboard Global Positioning System (GPS) and Inertial Navigation System (INS) measurements.
Abstract: An experiment is described to validate the concept of developing an autonomous integrated spacecraft navigation system using onboard Global Positioning System (GPS) and inertial navigation system (INS) measurements. Previous work by the authors (1988, 1990) has demonstrated the feasibility of integrating GPS measurements with INS measurements to provide a total improvement in spacecraft navigation performance, i.e., improvement in position, velocity and attitude information. An important aspect of this research is the automatic real-time reconfiguration capability of the system, which is designed to respond to changes in a spacecraft mission under the control of an expert system. >

52 citations


Patent
Karouby Philippe1
05 Oct 1993
TL;DR: In this article, a method of calculation by a GPS receiver of the position of a mobile in space and time relative to a predetermined frame of reference, the position is calculated from data supplied by at least four GPS satellites selected by the GPS receiver to form a calculation constellation.
Abstract: In a method of calculation by a GPS receiver of the position of a mobile in space and time relative to a predetermined frame of reference, the position is calculated from data supplied by at least four GPS satellites selected by the GPS receiver to form a calculation constellation. The method includes the step of estimating the error in the position calculation. This error is estimated by the GPS receiver for each calculated position. The estimated error therefore varies with the position of the mobile.

51 citations


Journal ArticleDOI
TL;DR: The results indicate that accurate rendezvous navigation using GPS only is quite feasible and using only observations of GPS satellites commonly visible from both rendezvouz spacecraft gives much better results than when all observations are used.
Abstract: A study of the application of the global positioning system (GPS) for precise real-time relative orbit determination during rendezvous and docking operations in low Earth orbit has been performed. It is a first attempt to analyze this complex problem, in which the relative navigation accuracy during the homing and closing phase of a typical rendezvous mission between the European space plane Hermes and the Columbus Free Flying Laboratory has been investigated. Results are presented of a covariance analysis of a hypothetical on-orbit real-time data processing system, based on Kalman filtering of pseudorange observations acquired by GPS receivers onboard the two spacecraft. The so-called reduced-dynamic technique was applied for the orbit determination of both spacecraft. A method is described to derive the relative position and velocity errors from the absolute state-vector covariances. Two data processing concepts have been investigated. It is shown that using only observations of GPS satellites commonly visible from both rendezvouz spacecraft gives much better results than when all observations are used. Overall, the results indicate that accurate rendezvous navigation using GPS only is quite feasible.

18 citations


Patent
17 Aug 1993
TL;DR: In this article, an aircraft with a SAR images of a target area is used to select a target in the target area from a known first position (P1) and the GPS coordinates of the position are determined and from which the range and monopulse angles of the target are computed.
Abstract: An aircraft (1) with a SAR images a target area (5) and selects a target in the target area from a known first position (P1) whereat the GPS coordinates of the position are determined and from which the range and monopulse angles of the target are computed to establish the location of the target in three dimensions with associated errors. The aircraft then flies to a second position (P2) whereat the GPS coordinates of the second position are determined and obtains another high resolution image of the target. Again, the range and monopulse angles of the target are computed. Because of the accuracy of the GPS-aided INS, computer aiding to the pilot will make this second designation much easier. Since the position vector between the two known positions can be provided with accuracy to within a few inches due to the accuracy of the GPS receiver with carrier phase tracking, the position of the target is determined largely by the range measurement accuracy of the radar and the two position locations. Since this establishes the location of the target in a GPS coordinate system relative to the position of the aircraft, absolute position errors typically associated with GPS navigation are canceled. The GPS guided weapon, when supplied with the target location in GPS coordinates, is then guided to the target with the high precision available in clear weather conditions. Since the radar and GPS are both fully functional in adverse weather as well as clear weather, there is provided an all-weather solution to precision weapon delivery.

15 citations


Journal ArticleDOI
TL;DR: In this article, an Inertial Navigation Systenl (INS) is described for robotics applications and error models for the inertial sensors are generated and included in an Extended Kalman Filter (EKF) for processing the data.

14 citations


Proceedings ArticleDOI
24 May 1993
TL;DR: This paper explores the possibility of improving navigation solutions and easing integration requirements by using non-linear filters based on direct solutions-to the GPS equations by using this MLE algorithm based on the use of statistical point estimation.
Abstract: This paper explores the possibility of improving navigation solutions and easing integration requirements by using non-linear filters based on direct solutions-to the GPS equations. An alternative approach to navigation with GPS and integration of GPS with other sensor systems is discussed. This two-stage method is based on the use of statistical point estimation. After discussing the underlying concept of two-stage estimation, problems encountered in the statistics of point estimation of position and bias from GPS solutions are surveyed. This is followed by a presentation of a closed form maximum likelihood estimator for position and bias based on the assumption of Gaussian errors. To the authors' knowledge, this MLE algorithm has not previously been published. Applications to the integration of the GPS with the INS are presented. >

Journal ArticleDOI
TL;DR: The real-time restitution of GPS time, with implementation of SA, is then improved to the level obtained without SA, and this paper gives details of the implementation of such a method together with a numerical test of its potential.
Abstract: The Global Positioning System is an outstanding tool for the dissemination of time. Equipped with C/A-code GPS time receivers, civil users may access the time scale GPS time, which is disseminated by the GPS satellites, and then the reference time scales UTC(USNO) and UTC. At a given instant, the restitution of GPS time through the satellite constellation presents a peak-to-peak discrepancy of several tens of nanoseconds without SA and several hundreds of nanoseconds with SA. The application of a Kalman filter to GPS timing data allows local access to GPS time through an estimation based on past data and updated at each new observation. The real-time restitution of GPS time, with implementation of SA, is then improved to the level obtained without SA. This paper gives details of the implementation of such a method together with a numerical test of its potential.

Proceedings ArticleDOI
24 May 1993
TL;DR: In this paper, the authors discuss the formulation of two such techniques for a cascaded GPS-INS Kalman filter integration, which is an integration in which the navigation solution from a GPS receiver is used as a measurement in the filter to estimate inertial errors and instrument biases.
Abstract: Filter robustness is defined as the ability of the GPS-INS Kalman filter to cope with adverse environments and input conditions, to successfully identify such conditions and to take evasive action. This paper discusses the formulation of two such techniques for a cascaded GPS-INS Kalman filter integration. This is an integration in which the navigation solution from a GPS receiver is used as a measurement in the filter to estimate inertial errors and instrument biases. The first technique presented discusses the handling of GPS position biases. These are due to errors in the GPS satellite segment, and are known to be unobservable. They change levels when a satellite constellation change occurs, at which point they introduce undesirable filter response transients. The paper presents a method of suppressing these transients. The second technique presented deals with the proper identification of the filter measurement noise. Successful formulation of the noise statistics is a factor vital to the healthy estimation of the filter gains and operation. Confidence in the formulation of these statistics can lead to the proper screening and rejection of bad data in the filter. The paper discusses a method of formulating the filter noise statistics dynamically based on inputs from the CPS and the INS. >

24 Sep 1993
TL;DR: In this paper, a system architecture has been developed that achieves tightly-coupled GPS/INS integration, while simultaneously simplifying the task of bringing compo-nents together and verifying their integration.
Abstract: A system architecture has been developed that accomplishes tightly-coupled GPS/INSintegration, while at the same time simplifying the task of bringing compo- nents together and verifying their integration. The simplified integration can be expected to make the systems affordable and available to a wider range of users than is currently possible. The objective of the work reported here was to prove out the integration concept, and to validate the major hardware and soft- ware components, by demonstrating an actual prototype. An Allen Osborne Associates, Inc. (AOA)TurboRogue GPS receiver was optimally integrated with an Inertial Science, Inc. (ISI) inertial navigation system using the integration concept and GPS/INS integration software developed by Don Knight. GPS/INS van testing was conducted, resulting in a verification of functionality and accuracy of the prototype. Test methods and results are described. Akey aspect of the prototype verification was the availability of a full GPS constellation. In two hours of van testing, with the van in motion, with an average of 6.7 satellites in track, and with an atomic clock in the van, the actual, measured differential delta ranges converged on a solution for van speed and heading with an RMS accuracy of 2 mm/set, or about 0.004 mph (four one thousandths of a mile per hour), The quantity and quality of GPS data enabled rapid calibration and alignment of the INS, using a Kalman fdter, and provid- ed an extremely accurate truth reference. That, in turn, allowed integration testing to be completed quickly, and it avoided having to resort to some other system, such as a laser ranging system, to serve as truth reference. What has not beenaccomplished at this time is demonstration of the whole system executing in real-time, and the use of INS-derived estimates of GPS Doppler in order to improve the receiver’s noise rejection, and to improve the reacquisition of signals that have been interrupted. The significance of this work is that tightly-coupled GPS/INS systems may becomemuch easier to build, and that, in turn, would benefit both users and suppliers by expanding thenumber and diversity of optimal GPS/INS systems in use.

Patent
06 May 1993
TL;DR: In this article, the authors proposed to eliminate the hourly error of the inertia sensor of an inertial navigation system so as to improve the accuracy of the sensor by correcting first navigation data which contains errors generated by the inertia sensors by using second navigation data from a GPS navigation system.
Abstract: PURPOSE: To eliminate the hourly error of the inertia sensor of an inertial navigation system so as to improve the accuracy of the sensor by correcting first navigation data which contains errors generated by the inertia sensor by using second navigation data from a GPS navigation system. CONSTITUTION: First navigation data 1a from an inertial navigation system 1 and second navigation data 3a from a GPS navigation system 3 are inputted to a comparing means 2 and the means 2 compares the data 1a and 3a with each other and inputs the difference between the two data to a state estimation filter 4 as an error 2a. The filter 4 calculates the estimated errors of an inertia and GPS sensors and feeds back the calculated errors to the systems 1 and 3 as estimated sensor errors 4a and 4b. When these operations are repeated, the accuracy of the navigation data la and 3a can be improved. COPYRIGHT: (C)1994,JPO

Proceedings ArticleDOI
09 Aug 1993
TL;DR: A trajectory reference system based on the Global Positioning System can be used instead of conventional radars during missile flight tests and is found to provide superior estimates of the IMU errors.
Abstract: A trajectory reference system based on the Global Positioning System (GPS) can be used instead of conventional radars during missile flight tests. The high quality of the GPS-based trajectory reference makes it useful for evaluating the performance of the missiles' Inertial Measurement Units (IMUs). Such a system was installed and flight tested on two recently launched ballistic missiles. The GPS hardware configuration used on these flights is described. A Kalman filter approach is used to estimate individual IMU errors based on the GPS range and delta range data. The ability of the GPS-based system to identify IMU errors is compared to that of radar; GPS is found to provide superior estimates of the IMU errors.

31 Dec 1993
TL;DR: In this paper, an airborne test using a differential GPS-INS system in a twin Otter was conducted by Sandia National Laboratories to assess the feasibility of using the integrated system for cm-level position and cm/s velocity.
Abstract: An airborne test using a differential GPS-INS system in a Twin Otter was conducted by Sandia National Laboratories to assess the feasibility of using the integrated system for cm-level position and cm/s velocity. The INS is a miniaturized ring-laser gyro IMU jointly developed by Sandia and Honeywell while the GPS system consists of the NovAtel GPSCard{trademark}. INS position, velocity and attitude data were computed using Sandia`s SANDAC flight computer system and logged at 4 Hz and GPS data was acquired at a 1 Hz rate. The mission was approximately 2.5 hours in duration and the aircraft reached separations of up to 19 km from the base station. The data was post-processed using a centralized Kalman filter approach in which the double differenced carrier phase measurements are used to update the INS data. The INS position is in turn used to detect and correct GPS carrier phase cycle slips and also to bridge GPS outages. Results are presented for the GPS-only case and also for integrated GPS/INS.

Proceedings ArticleDOI
12 Oct 1993
TL;DR: In this paper, the authors proposed using odometry as opposed to an Inertial Navigation System (INS) to improve the overall system performance by combining INS and odometry signals into an optimal, or at least more robust, estimation system.
Abstract: It is expected that an Inertial Navigation System (INS), when used on a land vehicle, would provide a superior position estimate to that which would be determined using odometry. There are a number of benefits to using odometry as opposed to an INS technique, including high physical robustness and reliability of the encoders, low weight, power consumption and cost, and a zero time-dependent drift. It would seem logical to include some form of odometry on any autonomous surface vehicle. If an INS technique is to be implemented, then it follows that an attempt should be made to improve the overall system performance by combining INS and odometry signals into an optimal, or at least more robust, estimation system.


Patent
Karouby Philippe1
06 Oct 1993
TL;DR: In this paper, a GPS receiver calculates the spatial and temporal position of a moving object in a predetermined reference system, this position being calculated on the basis of data supplied by at least four satellites of the GPS system selected by the GPS receiver in order to form a so-called calculation constellation.
Abstract: Procedure whereby a GPS receiver calculates the spatial and temporal position of a moving object in a predetermined reference system, this position being calculated on the basis of data supplied by at least four satellites of the GPS system selected by the GPS receiver in order to form a so-called calculation constellation. This procedure includes a step of estimating the error made in the position calculation, this estimation being carried out by the GPS receiver for each calculated position, so that the estimation of the error made varies with the position of the moving object.


24 Sep 1993

Proceedings ArticleDOI
09 Aug 1993
TL;DR: In this article, two new methods are developed to improve the sensitivity of the failure detection system, where the chi-square test is used to monitor the state estimates of the Kalman filter.
Abstract: In this paper, two new methods are developed to improve the sensitivity of the failure detection system, where the chi-square test is used to monitor the state estimates of the Kalman filter: (1) Using two state propagators, which are reset regularly with the data of the Kalman filter to increase their accuracy and so the detection sensitivity of the system, and used as the failure detection reference alternatively to avoid the risk of using the contaminated state propagator as the reference system for failure detection. (2) Monitoring the state estimates of the Kalman filter individually, so that the test statistics most seriously affected by the failures are utilized to enhance detection sensitivity. The effectiveness of the proposed approaches is demonstrated in the failure detection problem of a SDINS(Strapdown Inertial Navigation System)/GPS(Global Positioning System) integrated navigation system. The simulation results show that the failure sensitivity is remarkably increased. The system functions quite well to detect the soft failures in the gyros and accelerometers.

Proceedings ArticleDOI
09 Aug 1993
TL;DR: In this paper, an optimized linear ellipsoidal-bounded (LEB) filter was developed and applied to data obtained from a ground test using a combined INSIGPS configuration.
Abstract: An optimized Linear-Ellipsoidal-Bounded (LEB) filter has been developed and applied to data obtained from a ground test using a combined INSIGPS configuration. In this cascaded configuration, the filter receives eight outputs from the INS (accelerations, velocity, angles, altitude) and six outputs from the GPS (velocities and positions). The GPS measurements have included the effect of SA -of varying or unknown spectrum which, although likely to be estimated and compensated with some modelling techniques -at the expense of including extra state variables-, could also be dealt with the approach indicated in this article a t much less effort. An optimized formulation for the LEB filter is presented, in which the volume of the ellipsoid containing the estimation errors is minimized at every step or a t selected intervals. The SA effect is modelled as an unknownbut-bounded (UBB) noise process. Comparisons with an Extended Kalman filter (KF) show that KF innovations are not white and the LEB filter estimates are one order of magnitude smaller that those produced by the KF.

22 Jan 1993
TL;DR: A new class of ring laser gyro (RLG)-based strapdown inertial navigation systems has been established with the introduction of Honeywell's H-764G Integrated Embedded GPS/INS (GPWNS) as discussed by the authors.
Abstract: A new class of Ring Laser Gyro (RLG)-based strapdown inertial navigation systems has been established with the advent of Honeywell’s H-764G Integrated Embedded Global Positioning System/Inertial Navigation System (GPWNS). This system takes full advantage of precision pseudo-range and pseudo-range rate data available only from the embedded GPS receiver module which is integrated with the inertial data in a Kahnan filter. This synergistic approach results in superior operation in high dynamic, antenna shading, and jamming environments. As this paper will show, the H-764G successfully demonstrated this means of attaining the goal of low noise, precise navigation operation. Significant advantages exist in the embedded system mechanization when compared to the performance of stand-alone systems. Chief among these advantages is the outstanding performance obtained with fewer than four satellites in view; simplified installation; and reduced size, weight, and power. Through these distinctions, Honeywell has produced an embedded GPWINS that consistently demonstrates a more accurate navigation solution. This paper will serve to document the progressive development of the H-764G GPS/INS through a presentation of a brief system description, a look at the wide range of system applications, a review of a number of key discriminators. and finally, the exhibition of independently acquired test results from the Air Force’s Central Inertial Guidance Test Facility (CIGTF) and the Naval Research and Development division.

01 Sep 1993
TL;DR: In order to design and verify a precise, high update rate navigation system, a working model of Differential GPS has been developed including all of the major GPS error sources - clock differences, atmospherics, selective availability and receiver noise.
Abstract: : Precise navigation with high update rates is essential for automatic landing of an unmanned aircraft. Individual sensors currently available - INS, AHRS, GPS, LORAN, etc. - cannot meet both requirements. The most accurate navigation sensor available today is the Global Positioning System or GPS. However, GPS updates only come once per second. INS, being an on-board sensor, is available as often as necessary. Unfortunately, it is subject to the Schuler cycle, biases, noise floor, and cross-axis sensitivity. In order to design and verify a precise, high update rate navigation system, a working model of Differential GPS has been developed including all of the major GPS error sources - clock differences, atmospherics, selective availability and receiver noise. A standard INS system was also modeled, complete with the inaccuracies mentioned. The outputs of these two sensors - inertial acceleration and pseudoranges - can be optimally blended with a complementary Kalman filter for positioning. Eventually, in the discrete case, the high update rate and high precision required for autoland can be achieved.

01 Dec 1993
TL;DR: In this paper, the authors developed a multiple model EKF failure detection, isolation, and recovery (FDIR) algorithm using a Chi-square failure test to provide robust navigation solution to measurement failures.
Abstract: : An Inertial Navigation System(INS), the Global Positioning System(GPS), and a ground based transponder system(RRS) can all be used to provide the user with a navigation solution. Yet by integrating these three navigation systems with an extended Kalman filter(EKF), a navigation solution is attained that benefits from the information of all three subsystems. This research develops a multiple model EKF failure detection, isolation, and recovery(FDIR) algorithm using a Chi-Square failure test to provide robust navigation solution to measurement failures. The algorithm specifically counters failures in the GPS and RRS range measurements. Analysis is conducted using a Kalman filter development package known as the Multimode Simulation for Optimal Filter Evaluation (MSOFE). Both a large order truth model for the navigation system (in which a full 24 satellite constellations is modeled) and a reduced- order Kalman filter are developed. Results suggest that the multiple model algorithm can correct for all single measurement failures. Integrated navigation system, Extended kalman filter, Failure detection, Robust navigation.

01 Jan 1993
TL;DR: A comparison between Inertial Navigation Systems and Global Positioning Systems (GPS) as used in automatic vehicle location (AVL) systems is presented and the authors promote the use of INS in AVL systems given the continued improvement in accuracy for solid state gyroscopes and accelerometers and the cost reductions associated with them.
Abstract: This paper presents a comparison between Inertial Navigation Systems (INS) and Global Positioning Systems (GPS) as used in automatic vehicle location (AVL) systems. The authors promote the use of INS in AVL systems given the continued improvement in accuracy for solid state gyroscopes and accelerometers and the cost reductions associated with them. Additionally, the data provided by Inertial Measurement Units (IMU) can be utilized by a variety of existing vehicle systems to improve overall performance and reduce the total number of sensors required by the vehicle.

Journal ArticleDOI
TL;DR: In this paper, the authors derived general equations of position determination of a receiver which are based on analysis of the time-of-arrival of range measurement signals emitted from GPS satellites and of other related data measured or estimated.
Abstract: This paper derives general equations of position determination of a receiver which are based on analysis of the time-of-arrival of range measurement signals emitted from GPS satellites and of other related data measured or estimated. The least-squares method is used to integrate and process above data, and to determine the position and clock offset of the receiver. Analytical relations of DOPs (Dilutions of Precision) to the relative geometry of GPS satellites and the receiver are also derived by assuming the uniform deployment of GPS satellites. The results of the simulation study for satellite navigation performance under several cases of the operational environment are shown to evaluate the effectiveness of the satellite navigation algorithms based on the least-squares estimation proposed in this paper.

Proceedings ArticleDOI
25 May 1993
TL;DR: The mechanization satisfies the requirements for high velocity and attitude accuracy; high data rate; fault tolerance; and graceful degradation of accuracy and capability as equipment fails; extended firing orbits with large angles of attack and sideslip; and immediate recovery and reconfiguration following the loss of the primary mission computer.
Abstract: This paper describes the requirements, and the mechanization of the GPS-INS integration into the AC130U's integrated fire control system. Then gives a brief description of the basic avionic architecture and the modification made in support of this implementation. The paper will then discuss the mechanization and - innovative application of time proven Kalman filter techniques to solve the problems associated with data latency on the MlL-STD-l 553 bus, computer duty cycle limitations, and outline the requirements imposed by the AC-130U Gunship environment. The mechanization satisfies the requirements for high velocity and attitude accuracy; high data rate; fault tolerance; and graceful degradation of accuracy and capability as equipment fails; extended firing orbits with large angles of attack and sideslip; and immediate recovery and reconfiguration following the loss of the primary mission computer.