Abstract

Global Positioning System (GPS) provides a method for directly obtaining instantaneous position and velocity estimates using satellites-based passive range measurements. GPS is a whole day, all-weather, passive, satellite positioning system. Inertial Navigation System (INS) is a navigation aid system that uses a computer and Inertial Measurement Unite (IMU). IMU includes motion sensors and rotation sensors to continuously calculate relative position, orientation, and velocity. The integration of GPS/INS can help to overcome the limitations of the two systems providing integrated system better than either on a stand-alone basis. The integration of low-cost INS with dual frequency GPS has been widely studied and the same for the integration of tactical grid INS with low-cost GPS. However, during the last a few years, a number of low-cost GPS\low-cost INS integrated systems have been introduced and become popular in various engineering applications. However, reliable investigations into the advantages, limitations and quality of such integration level are still needed and more efforts are required, which will be the focus of this paper. The methodology followed in this paper for evaluating the integration of low-cost GPS/INS sensors depends on evaluating the two sensors individually and comparing the results with the integrated system. The results show that low-cost single frequency GPS receivers are able to provide a comparable accuracy level in both static and kinematic carrier phase differential GPS (DGPS). As for low-cost Micro-Electro-Mechanical System (MEMS)-based IMU, the accelerometers have provided instability comparing to gyros. The performance of gyros can be improved based on modelling the nearly-linear behaviour of the gyro drift. Tests show that the integration of low-cost GPS sensors with MEMS-based INS degrades the quality of gyro measurements and may not add any improvements to the quality of the individual GPS positioning.

Highlights

  • Global Positioning System (GPS) provides a method for directly obtaining instantaneous position and velocity estimates using satellites based passive range measurements

  • The tests show the high possibility of these receivers to be used as a rover and a base station to carry out low-cost static and kinematic differential GPS (DGPS)

  • The integration of low-cost L1-band based GPS receiver with low-cost Micro-Electro-Mechanical System (MEMS) based Inertial Navigation System (INS) has been evaluated in order to investigate the advantages of such integration level over the individual performance of the two sensors

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Summary

Introduction

Global Positioning System (GPS) provides a method for directly obtaining instantaneous position and velocity estimates using satellites based passive range measurements. Low-cost GPS receivers (single frequency) can provide carrier phase DGPS positioning based on L1 frequency; but the accuracy level tends to be degraded with increasing the baseline length as the ionosphere error becomes significant. GPS helps INS to reduce propagation of errors with time and to provide initial positioning and rotating This integration can be carried out in one of three main integration levels, namely: uncoupled, loosely coupled, and tightly coupled [2, 3, 7]. The integration of low-cost single frequency GPS with low-cost MEMS based INS will be evaluated in order to investigate whether this integration can help to overcome the limitations of the two systems and provide integrated system better than either on a stand-alone basis This level of integration has become more and more common and a number of integrated systems have been introduced during the last a few years. Reliable investigations into the integration of the two low-cost level sensors are still needed and more efforts in this area are required, which will be the focus of this paper

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