Global Positioning System Navigation System Research Articles

An Integrated Air Data / GPS Navigation System for Helicopters

In this study, the integration of two navigation systems Air Data System (ADS) and Global Positioning System (GPS) was aimed. ADS is a widely used navigation system which measures static and total air pressure and the air temperature. ADS has high sampling frequency and poor accuracy, on the other hand, another navigation system GPS has high accuracy compared to ADS but lower sampling frequency.Kalman Filter is used to integrate and minimize the errors of the two navigation systems. By this integration a navigation system with high sampling frequency and high accuracy is aimed. Another object is to calculate the wind speed with high accuracy.

English

The use of global positioning system (GPS) for precision guidance of weapons is being questioned due to its vulnerability of jamming and spoofing for non-military code users. In this paper a novel approach is proposed for guidance of weapons where use of GPS or other civilian Satellite-based navigation system is threatened. The proposed approach is modelled and simulated using SIMULINK for realistic trajectories and scenario. The results of simulation are validated with the actual GPS data.

A study of the adoption behaviour for In-Car GPS navigation systems

While In-Car Global Positioning System (GPS) navigation system is useful for drivers, the penetration rate remains relatively low. This study was based on the DeLone and McLean (D&M) Information System (IS) success model that incorporates reference group influences as belief-related constructs to assess the successfulness of In-Car GPS navigation systems. The research was done through a survey of 258 In-Car GPS navigation system subjects via the internet. The findings indicated that both D&M factors and reference group influences played important roles in measuring the success of GPS navigation devices. The results may provide further insights into GPS-related marketing strategies.

Kalman Filter-Based Integration of DGPS and Vehicle Sensors for Localization

We present a position estimation scheme for cars based on the integration of global positioning system (GPS) with vehicle sensors. The aim is to achieve enough accuracy to enable in vehicle cooperative collision warning, i.e., systems that provides warnings to drivers based on information about the motions of neighboring vehicles obtained by wireless communications from those vehicles, without use of ranging sensors. The vehicle sensors consist of wheel speed sensors, steering angle encoder, and a fiber optic gyro. We fuse these in an extended Kalman filter. The process model is a dynamic bicycle model. We present data from about 60 km of driving in urban environments including stops, intersection turns, U-turns, and lane changes, at both low and high speeds. The data show the filter estimates position, speed, and heading with the accuracies required by cooperative collision warning in all except two kinds of settings. The data also shows GPS and vehicle sensor integration through a bicycle model compares favorably with position estimation by fusing GPS and inertial navigation system (INS) through a kinematic model.

GPS satellite simulator signal estimation based on ANN

Multi-channel Global Positioning System (GPS) satellite signal simulator is used to provide realistic test signals for GPS receivers and navigation systems. In this paper, signals arriving the antenna of GPS receiver are analyzed from the viewpoint of simulator design. The estimation methods are focused of which several signal parameters are difficult to determine directly according to existing experiential models due to various error factors. Based on the theory of Artificial Neural Network (ANN), an approach is proposed to simulate signal propagation delay, carrier phase, power, and other parameters using ANN. The architecture of the hardware-in-the-loop test system is given. The ANN training and validation process is described. Experimental results demonstrate that the ANN designed can statistically simulate sample data in high fidelity. Therefore the computation of signal state based on this ANN can meet the design requirement, and can be directly applied to the development of multi-channel GPS satellite signal simulator.

An autonomous navigation scheme using global positioning system/geomagnetism integration for small satellites

This paper presents a low-cost scheme of an autonomous integrated global positioning system (GPS)/geomagnetism navigation system for small satellites to improve the performance of stand-alone GPS or geomagnetism navigation using the existing hardware equipment. In the paper, the use of the GPS and autonomous navigation systems based on magnetic field measurements (ANSMFM) to determine low Earth orbits (LEO) is discussed. The paper combines the GPS with the ANSMFM and constructs a new autonomous GPS/geomagnetism integrated navigation system (AGGINS) using two integration approaches: loosely and tightly coupled integrations. The improved extended Kalman filter completes the data processing for the optimal integration. The paper analyses the benefits of the AGGINS and finally gives simulation results that demonstrate the effectiveness and practicability of the method.

Classroom Note:The Global Positioning System and the Implicit Function Theorem

This paper provides an example of the implicit function theorem to the accuracy of global positioning system (GPS) navigation. The implicit function theorem allows one to approximate the timing accuracy required by the GPS navigation system to locate a user within a certain degree of precision.

Ionospheric specification from GPS data and the RIBG ionospheric propagation model

Global Positioning System (GPS) data for phase delay differential between Ll and L2 frequencies are analyzed by a model in which the combined effect of hardware and phase ambiguity terms is represented by a constant for each receiver‐satellite path and the ionospheric contribution is represented by the RIBG model (ray trace through the combined ICED (ionospheric conductivity and electron density), Bent, and Gallagher ionospheric models). RIBG contains a detailed global empirical climatological ionospheric model of the electron density versus height profile (EDP) from 80 km up to the plasmapause, which is combined with a full three‐dimensional ray trace propagation model. Discrete inverse theory (DIT) is used to fit the driving parameters of RIBG to about 2 hours worth of data from a single GPS receiver at various geographical locations. Validity is demonstrated by the ability of the GPS‐updated RIBG model to predict independent measurements of (1) vertical total electron content (TEC) over the ocean out to substantial distances from a GPS receiver, often in excess of 2000 km at midlatitudes, and (2) the electron density versus height profile (EDP). Performance variation with magnetic latitude is noted. Flexibility in RIBG to adjust different driving parameters for different parts of the EDP, in order to obtain a best fit of GPS data, benefits the EDP prediction. Implications of this approach for GPS navigation and other radio system applications are discussed.

Relationships between GPS-signal propagation errors and EISCAT observations

Abstract. When travelling through the ionosphere the signals of space-based radio navigation systems such as the Global Positioning System (GPS) are subject to modifications in amplitude, phase and polarization. In particular, phase changes due to refraction lead to propagation errors of up to 50 m for single-frequency GPS users. If both the L1 and the L2 frequencies transmitted by the GPS satellites are measured, first-order range error contributions of the ionosphere can be determined and removed by difference methods. The ionospheric contribution is proportional to the total electron content (TEC) along the ray path between satellite and receiver. Using about ten European GPS receiving stations of the International GPS Service for Geodynamics (IGS), the TEC over Europe is estimated within the geographic ranges -20°≤ λ ≤40°E and 32.5°≤ Φ ≤70°N in longitude and latitude, respectively. The derived TEC maps over Europe contribute to the study of horizontal coupling and transport proces- ses during significant ionospheric events. Due to their comprehensive information about the high-latitude ionosphere, EISCAT observations may help to study the influence of ionospheric phenomena upon propagation errors in GPS navigation systems. Since there are still some accuracy limiting problems to be solved in TEC determination using GPS, data comparison of TEC with vertical electron density profiles derived from EISCAT observations is valuable to enhance the accuracy of propagation-error estimations. This is evident both for absolute TEC calibration as well as for the conversion of ray-path-related observations to vertical TEC. The combination of EISCAT data and GPS-derived TEC data enables a better understanding of large-scale ionospheric processes.

Failure detection and isolation structure for global positioning system autonomous integrity monitoring

In this paper, a new failure detection and isolation (FDI) structure is investigated for global positioning system (GPS) integrity monitoring in an integrated inertial navigation system (INS)/GPS navigation system. In the structure, a bank of auxiliary integrated INS/GPS Kalman filters, each of them processing a subset of the GPS measurements, are applied to provide high-accuracy detection references. The failure detection is then undertaken by checking the consistency between the state estimate of the main integrated INS/GPS Kalman filter and the auxiliaries. Two state propagators are also included in the FDI structure to reliably isolate the failed GPS measurement. The two propagators are alternatively reset with the data of the Kalman filter to increase their accuracy and thereby the failure isolation performance. The failure isolation is realized by testing the consistency between the state estimates of the auxiliary Kalman filters and the state propagator. The simulation results show that the FDI structure is capable of not only detecting the presence of a malfunctioning satellite that results in a large range error, but also identifying which satellite is malfunctioning.

Global Positioning System Operational Control System Accuracies

In early 1985, an improved ground Operational Control System (OCS) will maintain the navigation service. Primary among the OCS improvements over past GPS navigation systems is a global network of ground antennas (to upload satellite navigation data) and tracking/monitor stations. In addition, a refined Kalman filter will continuously estimate the Global Positioning System (GPS) satellite ephemerides and clock phases and frequencies. Although the user-GPS interface remains unaltered, the accuracy of the GPS navigation service is expected to improve by a factor of three. Using real and simulated GPS pseudo range radiometric tracking data, The Aerospace Corporation has completed a detailed error analysis which shows that the satellite clock noise contributes more than 90 percent of the total satellite-to-user pseudo range error. If the number of OCS uploads is increased to three per day (as planned), then the accuracy of the navigation service is also expected to improve by nearly a factor of three because the clock-noise contribution to the range error increases linearly with time. Also, this analysis shows the consequence of satellite ephermeris uncertainties in the GPS navigation application.

The Global Positioning System and Its Application in Spacecraft Navigation

The paper presents an overview of the Global Positioning System (GPS) as well as a discussion of the user system parameters govering the design of a low-earth-orbit spacecraft GPS navigation system. A specific application, the Space Shuttle orbiter GPS navigation system, is discussed with particular attention given to its receiver/processor.