TABLE OF CONTENTS For many vehicles requiring a navigation capability, there are two basic but conflicting requirements to be considered by the designer, namely those of achieving high accuracy and low cost. This chapter examines the scope for satisfying these demanding requirements by using integrated navigation systems, in which strapdown inertial navigation systems are used in conjunction with other navigation aids. The variety of modern navigation aids now available is extensive and, coupled with advances in estimation processing techniques and high-speed computer processors, have resulted in greater application of integrated navigation systems in recent years.
As discussed in Chapter 12, the performance of an inertial navigation system is characterised by a time-dependent drift in the accuracy of the position estimates it provides. The rate at which navigation errors grow over long periods of time is governed predominantly by the accuracy of the initial alignment, imperfections in the inertial sensors that the system uses and the dynamics of the trajectory followed by the host vehicle. Whilst improved accuracy can be achieved through the use of more accurate sensors, there are limits to the performance that can reasonably be achieved before the cost of the inertial system becomes prohibitively large. Very expensive inertial navigation systems are incompatible with most applications except for those special strategic systems where there is no easy alternative, such as submarine navigation or other strategic platforms and missiles. However, as discussed in Chapter 15, alternative mechanisation techniques may be used to ease the demands on sensors' performance, whilst maintaining...
