Showing papers on "GPS/INS published in 2000"

Global Positioning Systems, Inertial Navigation, and Integration

Abstract: An updated guide to GNSS and INS, and solutions to real-world GPS/INS problems with Kalman filtering Written by recognized authorities in the field, this second edition of a landmark work provides engineers, computer scientists, and others with a working familiarity with the theory and contemporary applications of Global Navigation Satellite Systems (GNSS), Inertial Navigational Systems (INS), and Kalman filters. Throughout, the focus is on solving real-world problems, with an emphasis on the effective use of state-of-the-art integration techniques for those systems, especially the application of Kalman filtering. To that end, the authors explore the various subtleties, common failures, and inherent limitations of the theory as it applies to real-world situations, and provide numerous detailed application examples and practice problems, including GNSS-aided INS, modeling of gyros and accelerometers, and SBAS and GBAS. Drawing upon their many years of experience with GNSS, INS, and the Kalman filter, the authors present numerous design and implementation techniques not found in other professional references. This Second Edition has been updated to include: GNSS signal integrity with SBAS Mitigation of multipath, including results Ionospheric delay estimation with Kalman filters New MATLAB programs for satellite position determination using almanac and ephemeris data and ionospheric delay calculations from single and dual frequency data New algorithms for GEO with L1 /L5 frequencies and clock steering Implementation of mechanization equations in numerically stable algorithms To enhance comprehension of the subjects covered, the authors have included software in MATLAB, demonstrating the working of the GNSS, INS, and filter algorithms. In addition to showing the Kalman filter in action, the software also demonstrates various practical aspects of finite word length arithmetic and the need for alternative algorithms to preserve result accuracy.

Inertial navigation systems with geodetic applications

Abstract: Coordinate frames and transformations ordinary differential equations inertial measurement unit inertial navigation system system error dynamics stochastic processes and error models linear estimation INS initialization and alignment the global positioning system (GPS) geodetic application.

Relative GPS positioning using a single GPS receiver with internally generated differential correction terms

Abstract: A technique of accurately determining the relative position between two points, in real-time, using a single GPS receiver that makes measurements of signals transmitted from GPS satellites. A technique is applied where differential correction terms are computed as a location at an instant of time, and then applied to further times, after applying atmospheric delay adjustments, so that the position of the GPS receiver is determined accurately relative to the position at the original instant of time.

Fuzzy adaptive Kalman filtering for INS/GPS data fusion

Abstract: Presents a method for sensor fusion based on adaptive fuzzy Kalman filtering. The method is applied in fusing position signals from Global Positioning Systems (GPS) and inertial navigation systems (INS) for autonomous mobile vehicles. The presented method has been validated in a 3-D environment and is of particular importance for guidance, navigation, and control of flying vehicles. The extended Kalman filter (EKF) and the noise characteristics are modified using the fuzzy logic adaptive system, and compared with the performance of a regular EKF. It is demonstrated that the fuzzy adaptive Kalman filter gives better results, in terms of accuracy, than the EKF.

Efficient use of digital road map in various positioning for ITS

Abstract: There are many R&D improvements on positioning systems for ITS (intelligent transportation systems) adopting GPS, cellular phones or other communication systems. But, a position from any signal is always corrupted to a few meters through several hundreds of meters because of multipath, atmospheric delay, NLOS (non-line-of-sight), low DOP and so on. When the positioning systems are employed for ITS, a digital road map can be used together to display their navigation solutions in most ITS applications. Due to the fact that land-vehicles almost always run on roads, most of CNS (car navigation systems) translate the measured position onto a road. This methodology called map-matching, if it depends on a contaminated position due to white noise and biased error, has not only low accuracy but also the road ambiguity problems in some crossroads. Therefore, this paper presents an efficient use of an advanced map-matching in order to get a more improved accuracy, which estimates a large bias being the main source of errors and corrects a vehicle's position. It is composed of a modeling of biased error and filtering by a Kalman filter. We have applied the proposed map-matching to not only GPS navigation but also CDMA location. The proposed approach represents that in addition to its original visual display, an accurate digital road-map can improve the positioning accuracy effectively by correcting the vehicle's position.

GPS roadside integrated precision positioning system

Abstract: A real-time integrated navigation system with 2-cm position accuracy was developed using commercial off-the shelf (COTS) equipment including inertial sensors and differential Global Positioning System (GPS) receivers, and was demonstrated for transportation applications with an emphasis on lane departure detection. A 900-MHz radiofrequency communications link transmits GPS base station range and carrier phase measurements to a GPS receiver on the vehicle. The GPS receiver calculates the vehicle position relative to the surveyed base location. The loosely coupled eight-state extended Kalman filter with 10-Hz navigation aids provides smoothed position information between 2-Hz GPS updates and provides graceful degradation in the presence of GPS blockages or communication dropouts. Currently, the navigation aids include anti-lock braking system wheel turns, electronic compass heading and pitch, and map vertical height. Data acquisition and Kalman filtering systems were developed to handle real-time processing and recording of all instrument data for further post-test system evaluation to determine the optimum configuration. An accurate rapid survey and map representation approach for measuring lane boundaries was validated using a vehicle, demonstrating inherit repeatability by the GPS positioning system. Real-time lane departure monitoring was developed. A video camera was installed to assist in accurate surveying and real-time system validation. This GPS-based positioning system is suitable for highway speeds during all weather conditions. It can be extended to other collision avoidance, drowsy driver awareness, advanced curve or intersection warnings, SOS, tracking, automated control, fast precision road mapping, and traffic management applications.

Self-contained positioning method and system thereof for water and land vehicles

Abstract: A positioning method and system for water and land vehicles is disclosed for highly accurate and self-contained operation. In which, an inertial navigation system (INS) is built on the micro MEMS (MicroElectroMechanicalSystem) IMU that is the core of the position determination system. To compensate the error of the INS, multiple navigation sensors are integrated into the system. The magnetic sensor is used as a magnetic field sensor to measure the heading of the vehicle. The odometer is used to measure the distance when the vehicle is on land. An automated Zero velocity updating method is used to calibrate the ever increasing INS errors. When the vehicle is in the water, a velocimeter is used to measure water speed for the INS aiding.

Method and apparatus for achieving sole means navigation from global navigation satelite systems

Abstract: A sole means global navigation apparatus adapted for use on an aircraft includes a GPS receiver to provide GPS measurement data and an inertial sensor system adapted to provide inertial translational and rotational data which during time periods is independent of the GPS position data. A navigation system coupled to both of the GPS receiver(s) and the inertial sensor system determines a navigation solution as a function of both the condition of the GPS satellite data and the uncertainty in the Inertial data. An augmentation system coupled to the navigation solution determining system is used to increase the accuracy and/or integrity of the GPS/inertial sensor, thereby achieving style means navigation requirements.

Process and system of coupled real-time GPS/IMU simulation with differential GPS

Abstract: A coupled real-time GPS/IMU simulation method with differential GPS includes the steps of receiving real-time trajectory data from a 6DOF trajectory generator and generating GPS simulated measurements (rover and reference) and inertial measurement unit simulated electronic signals based on the real GPS models and IMU models, respectively, and injecting those simulated data into an on-board integrated GPS/INS (global positioning system/inertial navigation system). Therefore, the coupled real-time GPS/IMU simulation method with differential GPS can be applied to evaluate the performance of the integrated GPS/INS in the area of high accuracy positioning in addition to the regular evaluation (one receiver mode).

Comparison of INS vs. Carrier-phase DGPS for attitude determination in the control of off-road vehicles

Abstract: This paper compares the use of an inertial navigation system (INS) and a multiple GPS antenna system for attitude determination of an off-road vehicle. The INS system currently provides a less expensive attitude solution than the multiple GPS antenna system. Additionally, the INS system does not suffer from GPS errors resulting from multipath and antenna blockages. A Kalman filter incorporates the INS measurements with centimeter-level carrier-phase differential GPS (DGPS) measurements from one position antenna for complete position and attitude estimation of an off-road vehicle. The centimeter-level accuracy of DGPS allows for precise calibrations of the INS system for accurate attitude estimation. The paper shows that a low-cost INS system is capable of providing the attitude accuracy necessary for centimeter-level control of an off-road vehicle. Results of using the INS system in conjunction with DGPS position measurements to autonomously control a farm tractor are presented.

Enhancement of signal-detection capability of GPS systems

Abstract: Estimated Global Position System (GPS) navigation data is used to increase the signal integration interval. In one embodiment, a WAG (wireless assisted GPS) server receives GPS signals and demodulates the navigation data modulated onto the GPS signals. The WAG server utilizes known features of the demodulated navigation data to generate estimated navigation data for the satellite. This estimation can be made several seconds or even minutes ahead of time. The wireless terminal uses this estimated navigation data to perform a data wipe-off operation to enable the integration interval to be increased (e.g., beyond 20 ms), thereby increasing overall signal-detection sensitivity at the wireless terminal. In another embodiment, information from strong GPS signals is used to detect weak GPS signals from other satellites. In this embodiment, strong GPS signals are received directly by the wireless terminal from the satellites. After strong GPS signals have been detected, the strong GPS signals are demodulated to compute satellite ephemerides including navigation data. The demodulated navigation data is then matched with known features of the navigation data to estimate the navigation data for weak GPS signals. The estimated navigation data is then used to increase the integration interval for weak GPS signals so that weak GPS signals can also be detected at the wireless terminal.

Enhancing the integrity of integrated GPS/INS systems by cycle slip detection and correction

Abstract: Satellite navigation systems are widely used for high accuracy applications. Before the carrier phase observable can be utilized as the most accurate ranging information its inherent integer cycle ambiguity must be resolved. The algorithms for ambiguity resolution and carrier phase positioning rely on the ambiguities being constant. However, high dynamics, shadowing or multipath may cause so-called cycle slips which would deteriorate the accuracy if remained undetected. A new method was developed using an integrated system consisting of an inertial measurement unit and a differential GPS (Global Positioning System) sensor. With this method the integrity of cycle slip free carrier phase information is greatly enhanced which was demonstrated in driving tests.

Accurate orientation for airborne mapping systems

Abstract: Stringent requirements on the accuracy of attitude determi- nation are currently a major challenge for strapdown INS/GPS integration, which is at the core of self-contained airborne remote sensing and mapping systems. This paper reviews the error models for INS/GPS integration and focuses i n detail on designingfiltering methodsfor improvingattitudeaccuracyin the bandwidth in which an inertial system does not benefit from frequent GPS position/velocity updates. Several fltering methods are designed based on the spec- tral analysis of the raw inertial signal in a dynamic environ- ment. These include a spectral technique for dither spike removal and a class of low-pass finite-impulse-response (FIR] filters operatinginforward/backward mannerfor achieving zero phase distortion. The orientation performance of the whole system with different filters i s evaluated b y comparing it to the "true" attitude information provided by a photo- grammetric block adjustment. Results show clearly that the choice of an appropriatefilter is decisivefor attitude accuracy. Overall, the INS/GPS integration combined with the most suitable pre-filtering method agrees with the external orien- tationreferenceto0.005"(19')RMS overthewholetestperiod, while the flight-line consistency is typically 0.003" (1U')RMS. The best filter in the comparison has an i?MS seven times smaller than the Butterworth filter which i s frequently applied i n the industrial designs of INS.

Method and apparatus for maintaining the integrity of spacecraft based time and position using GPS

Abstract: A method and apparatus for maintaining the integrity of spacecraft based time and position using GPS (11) is disclosed. A GPS receiver is provided with a Receiver Autonomous Integrity Monitor (RAIM) processor (12) and a Kalman filter (14). GPS signals are received from at least four GPS satellites and processed in the GPS receiver to provide time and position information. Periodically, an extended fault vector is formed in the Kalman filter with propagated open-loop position and velocity measurements. The extended fault vector is used to isolate and remove failing GPS satellites.

Apparatus and method for minimizing multipath signal errors during tracking of GPS satellite signals

Abstract: A digital GPS receiver includes electronics to detect the presence of multipath GPS signals, determine the direction from which they are received at a multi-element GPS phased array antenna, adaptively generate an antenna pattern to provide gain in the direction of the desired GPS satellite signal, and to apply nulls in the direction of the detected GPS multipath signals. This adaptively-generated antenna pattern is applied to the signals received at the elements of the GPS phased array antenna to provide a composite signal to each of the processing channels of the digital GPS receiver, optimized for the particular GPS satellite being tracked by a corresponding channel. The undesirable multipath GPS signals are thereby excised from the inputs to the processing channels of the digital GPS receiver, and the desired direct signal is reinforced, thus enabling tracking loops within the digital GPS receiver to make highly accurate observations of the code and carrier phase using conventional signal processing techniques.

Airborne vector gravimetry using GPS/INS /

Abstract: This report was prepared by Jay Hyoun Kwon, a graduate student, Department of Civil and Environmental Engineering and Geodetic Science, under the supervision of Professor Christopher Jekeli.

System and method for measuring distance between two objects using received satellite transmitted data

Abstract: A global position satellite receiver (GPS receiver) is located in a fixed, undefined location on or in the vacinity of a golf course. The distance and direction between the fixed GPS receiver and a pin on the green of a hole on the golf course is measured using conventional distance and direction measuring apparatus. This is a first measured leg. A mobile GPS receiver, with computer, is on the golf course. A golf ball is on the fairway of the hole. The fixed GPS receiver receivers first global position satellite signals (GPS Data) from global position satellites in orbit above the earth, the first GPS Data defining a location for the fixed GPS receiver. The mobile GPS receiver receives second GPS Data from the global position satellites which defines a location for the mobile GPS receiver. Both sets of GPS Data are identically contaminated and both location definitions are unreliable, in accuracy. The first GPS Data and the second GPS Data are mathematically calculated to derive the distance and direction between the fixed GPS receiver and the mobile GPS receiver. This is a derived leg. The distance and direction between the mobile GPS receiver and the golf ball on the fairway are measured using conventional distance and direction finding apparatus. This is a second measured leg. The derived leg and the second measured leg are mathematically combined to calculate the distance and direction between the fixed GPS receiver and the golf ball. This is the first calculated leg. The first measured leg and the first calculated leg are mathematically combined to calculate the distance and direction between the golf ball on the fairway and the pin.

A multi-antenna GPS system for local area deformation monitoring

Abstract: A new method of using GPS for monitoring local area deformations such as landslides is presented. Unlike the standard method of using GPS for deformation monitoring where a GPS receiver is required for each point to be monitored, the new method allows multiple points to be monitored with one receiver. A system that implements the concept has been developed. It uses a specially designed electronic component that allows a number of GPS antennas to be linked to a single GPS receiver. The receiver takes data sequentially from each of the antennas attached to the receiver. A distinctive advantage of the approach is that one GPS receiver can be used to monitor more than one point. The cost per monitored point is therefore significantly reduced. The design of the system, as well as the data management and processing strategies will be introduced in detail. Results from some preliminary tests will also be given.

Improvement of the positioning accuracy of a software-based GPS receiver using a 32-bit embedded microprocessor

Abstract: This paper describes the improvement of the positioning accuracy of a GPS receiver, using software to apply the GPS to compact, hand-held devices. Differential GPS (DGPS) with a software FM demodulator, and a modified Kalman filter is proposed and applied to a GPS receiver. The positioning accuracy is, 35 m with a standalone GPS, 9 m with DGPS and 15 m with a Kalman filter. With both methods, the positioning accuracy is drastically improved to 2 m.

Position detector using gps and network assist-ready gps position detecting system using it

Abstract: PROBLEM TO BE SOLVED: To provide a GPS position detector capable of selectively setting a plurality of previously prepared positioning functions for use according to preference of a user. SOLUTION: This position detector 10 using GPS having a GPS positioning function and a communication function is provided with a positioning mode selection means 10c for selectively setting an optional positioning mode from a plurality of previously prepared GPS modes.

Reduction of time error in GPS localization without a highly accurate clock

Abstract: A method for minimizing time error uses a drift-susceptible time clock at the receiver carried by an asset to be tracked in a high-accuracy reduced-order GPS asset localization system. Long-term accuracy of the time clock is maintained by periodically re-synchronizing the clock with the master GPS time clock so that absolute asset time clock errors are kept below a known limit over the wide temperature ranges expected in the asset tracking application. This is accomplished with only a short GPS signal reception time; i.e., GPS frame synchronization and time-stamp decoding are not needed, and the asset position ambiguity associated with using GPS data-bit or code-bit edges as signal time references is eliminated.

Navigation device and gps receiver

Abstract: PROBLEM TO BE SOLVED: To accurately correct GPS data and precisely calculate the present position by time-wise synchronizing GPS data and sensor data in consideration of the time required for the geodetic calculation of the GPS data. SOLUTION: The present position is precisely calculated by time-synchronizing a GPS 20 and sensors in consideration of the delay time to the data output from the data acquisition of the GPS 20. This navigation device is provided with the GPS receiver (GPS) 20 provided on a moving body such as a vehicle, acquiring the data transmitted from a GPS satellite, and output the GPS data after geodetic calculation, various sensors such as a gyroscope sensor 26 or the like detecting the state of the moving body, a sensor data controller 25 controlling the data from various sensors, and a CPU 10 setting the internal system time based on the time required for the geodetic calculation by the GPS receiver 20 and controlling the detection results from the sensors by using the set system time.

Design and Validation of an Accurate GPS Signal and Receiver Truth Model for Comparing Advanced Receiver Processing Techniques

Abstract: : Recent increases in the computational power of computers and digital signal processors have made possible new, novel signal tracking techniques in GPS receivers. One such technique is known as Direct Correlators Output Processing (DCOP). This technique replaces individual traditional tracking loops with a single Kalman Filter, which jointly processes the received signals while exploiting their correlated noises. DCOP is innovative in its potential to replace the tried and true classical signal tracking loops. It is also an enabling technology for ultra-tightly coupled GPS/INS (Global Positioning System/Inertial Navigation System). Potential benefits of these new tracking techniques include an order-of-magnitude improvement in positional accuracy in environments of jamming and high dynamics. However, such performance gains are typically based on software simulations of conceptual GPS receiver designs, not working prototypes. Simulating these new designs requires the modeling of GPS signals and receiver tracking loops, instead of the traditional pseudorange and carrier-phase measurements, which many proven GPS simulation software packages accurately model. The purpose of this research has been to develop an accurate, user-friendly, and customizable GPS signal and receiver model to use for a fair and unbiased evaluation of advanced receiver designs. The result of this research is a Matlab GPS signal simulator, QR a Simulink GPS receiver model implementing true receiver DSP processing, and a Matlab high-speed signal/receiver model that approximates the signal simulator and receiver model.

Global positioning system and global positioning method with improved sensitivity by detecting navigation data inversion boundaries

Abstract: A Global Positioning System (GPS) forms a C/A code sequence by summing, beginning from a polarity inversion boundary determined by a correlation peak position detector, chips at corresponding positions in PN frames constituting each bit of navigation data; calculates pseudo ranges by computing correlation between the C/A code sequence and a reference C/A code sequence generated by the GPS terminal; and determines the position of the GPS terminal using the pseudo ranges and navigation data. The navigation data detected inside the GPS terminal is used when a received electric field detected by a received electric field intensity detector is greater than a threshold level, and the navigation data received from an external system is used when the received electric field is below the threshold level. Thus, the number of PN frames to be integrated is limited because the polarity inversion boundaries of the navigation data are detected, and hence the sensitivity (S/N ratio) is sufficient. Communication between a terminal and a base station is not always required for determining the position because the GPS terminal does not always obtain the Doppler information from the base station, reducing communication cost.

High-accuracy, high-frequency differential carrier phase GPS aided low-cost INS

Abstract: This article describes experimental results for a real-time, carrier phase, differential Global Positioning System (GPS) aided inertial navigation system (INS). The INS uses inexpensive solid state inertial sensors sampled and integrated at 150 Hz with differential GPS carrier phase measurements as corrections via a complementary filter at 1 Hz. Therefore, the implementation achieves 150 Hz, vehicle state estimates with position accuracy at the centimeter level. Such navigation systems have many application possibilities (e.g., aviation and precision flight, automated mining, precision farming, dredging, satellite attitude control, and automotive or train control). The experimental results described herein are the result of automated vehicle testing on the high occupancy vehicle lanes of the I-15 near San Diego in July 1999.

AUV positioning using bathymetry matching

Abstract: A research concern in AUV positioning is the constraint of INS error growth; approaches to this include surfacing for GPS fixes, terrain matching methods and acoustic transponder systems. The paper presents a positioning technique for AUV's that exploits existing bathymetric data in an operation area. Unlike many terrain matching approaches, which do positioning using distinct ocean bottom features, this method generates a position estimate by comparing the in-situ measured depth at the position of the AUV with available bathymetry data in the immediate area. This builds on contemporary AUV INS/VL navigation systems by incorporating a maximum likelihood estimate of position. Particular emphasis is placed on the design of the maximum likelihood estimator module which produces point-wise position estimates and typically contains a large error component with many outliers. This estimate is merged with the output of the AUV's INS/VL system which constrains the INS drift. Further position accuracy and faster convergence to the correct position can be achieved by incorporating a single slant range measurement from the AUV to a fixed location. The slant range is used as external constraint on both the INS and the MLE. The paper describes the implementation of this approach and the results of simulation studies.

High Precision Georeferencing using GPS/INS and Image Matching

Abstract: The registration and geometric recti cation of airborne scanner imagery is an essential prerequisite for the processing and analysis of this type of images The Digital Photogrammetric Assembly (DPA) is an airborne camera consisting of three pan-chromatic line arrays for stereo imaging and four line arrays for multi-spectral imaging For georeferencing the sensor system is completed by a module consisting of a di erential GPS receiver con guration and an Inertial Navigation System (INS) Additionally, due to the along-track stereo capability of the camera error terms for position and attitude can be estimated by photogrammetric constraints utilizing ground control points and corresponding image points In order to get a high accuracy position and attitude are determined by integrating all available information (GPS, INS and stereo image data) Within the article the geometric processing of the high precision and high resolution scanner imagery will be described and results of the performed test ight in October 1996 will be presented