From Strapdown Inertial Navigation Technology, 2nd Edition

Overview

The accuracy of an inertial navigation system is often expressed as a position uncertainty after a given period of navigation, or on reaching a given destination. Alternatively, it is expressed in terms of the rate at which the navigation error builds up with time, in nautical miles per hour for instance. The actual form of expression used for this overall accuracy figure depends upon the application. For example, for an inter-planetary missions, the accuracy refers to the desired point of closest approach to the 'destination' planet. For navigation in the vicinity of the Earth, it is usually the errors in two dimensions which are of most interest, the along-track and cross-track position errors over the surface of the Earth. These errors are often combined to yield a single number which expresses navigation accuracy after a given navigation time, the circular error probable (CEP) or circular probable error (CPE) as it is sometimes called. Essentially, this defines a circular area within which the navigation system estimates its true position to be, with a certain probability. The 50 per cent CEP is a frequently quoted figure. When the probability value is not stated, it usually means a 50 per cent value should be assumed.

Consider now the composition of this navigation performance figure. In practice, navigation errors propagate owing to a large number of error sources which include alignment errors, a variety of inertial sensor errors and errors attributable to computational inaccuracy. In general, each errors may be regarded as comprising...

Copyright The Institution of Electrical Engineers 2004 under license agreement with Books24x7

Products & Services
Inertial Navigation Systems
Inertial navigation systems use a combination of accelerometers and angular rate sensors (gyroscopes) to detect altitude, location, and motion. They may also be capable of detecting attitude, position, velocity, temperature, or magnetic field.
GPS Chips and Modules
GPS chips and modules compare signals from several geo-positioning satellites to determine position on the Earth's surface. GPS is an acronym for global positioning system.
Navigational Instruments
Navigational instruments include products such as distance meters, range finders and mapping systems.
Spectroradiometers
Spectroradiometers are used to measure the spectral power distributions of light sources, monitors, and other illuminants.
Spectrum Analyzers and Signal Analyzers
Spectrum analyzers and signal analyzers display raw, unprocessed signal information such as voltage, power, period, wave shape, sidebands, and frequency. They can provide the user with a clear and precise window into the frequency spectrum.

Topics of Interest

Overview Practical inertial navigation systems may take a variety of forms. These forms generally fall into one of two basic categories, stable platform systems; strapdown systems. Although the...

12.1 Introduction In a practical implementation, the accuracy to which a strapdown inertial navigation system is able to operate is limited as a result of errors in the data which are passed to it...

9.5.2 Navigation Error Propagation The dynamics of INS error propagation are strongly influenced by the fact that gravitational accelerations point toward the center of the earth and decrease in...

14.1 Introduction The objective of this chapter is to apply the various aspects of strapdown inertial navigation, discussed in the preceding chapters, to a design example. Before any design of an...

INTRODUCTION There are five basic forms of navigation: Pilotage, which essentially relies on recognizing landmarks to know where you are and how you are oriented. It is older than humankind. Dead...