From Strapdown Inertial Navigation Technology, 2nd Edition


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...

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.
Flight Management Systems
Flight management systems are multipurpose avionic computer systems that display navigational information and manage flight plans. They receive data from various sensors to interpret the position, heading, and speed of an aircraft and provide information regarding the aircraft's flight plan, destination, and logistics.
Inertial Measurement Units (IMU)
Inertial measurement units (IMUs) determine location via integrated gyroscopes and accelerometers that detect the distance and direction traveled over a period of time.
Navigation Lights
Navigation lights are colored illumination devices used on aircraft, watercraft, and spacecraft. They are used to alert other crafts or vessels of the signaling craft's position, status, and/or heading.
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 initialism for global positioning system.

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...