Avionics Navigation Systems, 2nd Edition

3 Multisensor Navigation Systems

3.1 INTRODUCTION

Multisensor navigation is the process of estimating the navigation variables of position, velocity, and attitude from a sequence of measurements from more than one navigation sensor. There are essentially two broad categories for sensors used in avionics suites for navigation and related functions: dead-reckoning sensors and positioning sensors. The processing equations for these are given in Chapter 2.

Dead-reckoning sensors provide a measure of acceleration or velocity with respect to an Earth-referenced coordinate system, consequently requiring integration with respect to time to provide vehicle position with respect to the Earth. Examples of these types of sensors are inertial systems (Chapter 7), Doppler radars (Chapter 10), and air-data sensors (Chapter 8). The latter two require an attitude and heading reference (AHRS) or an inertial system (INS) to provide the required angular orientation with respect to the Earth.

Positioning sensors provide a position measurement that can be related to Earth-referenced coordinates. Examples of these sensors are radio systems such as the terrestrial-based Loran and the satellite-based Global Positioning System (GPS) (Chapters 4 and 5) which provide the position of the antenna in geodetic coordinates. A star-tracker can also be used for fixing position when its orientation with respect to the Earth is determinable through some means such as an AHRS or INS.

This chapter describes filtering ...