From Strapdown Inertial Navigation Technology, 2nd Edition

15.6 Geodetic and Geophysical Measurements and Observation of Fundamental Physical Phenomena

An accurate model of the shape of the Earth is a very important aspect of any terrestrial navigation system, as has already been discussed in Chapter 3. However, fluctuations in the rotational characteristics of the Earth also have an impact on the potential accuracy of terrestrial navigation systems, including those that use precision GPS data. Measurement of other changes to the behaviour of the Earth may be used to predict seismic events, such as earthquakes.

Many factors produce small fluctuations in the characteristics of the Earth's rotational parameters. The principal factors that induce these fluctuations are;

  • continental drift;

  • motion of the moon and its phases;

  • movement of the subterranean magma in the Earth's core;

  • tides;

  • weather.

Chapter 13 and Appendix D considers the operation and use of the popular satellite-based navigation systems, which offer the potential for high-precision navigation for all types of vehicles and platforms. The basis of the technique is the constellation of satellites in geo-stationary orbits locked in a particular known position above the Earth. Consequently, errors in the estimated position of a navigation system's receiver will occur owing to the displacement of the constellation of satellites, resulting from the fluctuations of the Earth's rotational motion. Hence, changes in these characteristics of the motion of the Earth need to be measured and understood, so that an appropriate compensation technique can be applied.

One technique that is being investigated for the measurement and monitoring of the Earth's...

Products & Services
Geophysical Instruments
Geophysical instruments are used for geological study, including rock and soil mechanics, core analysis and surveys of the earth.
Satellites are manmade objects placed in orbit above the Earth for a variety of civil, scientific, and military applications, such as communications, environmental monitoring, navigation, and reconnaissance.
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.

Total Stations, Theodolites, and Transits
Theodolites and Transits are used for the accurate measurement of features, orientation and absolute positioning of large scale objects in engineering, construction, mapping, industry, defense and other applications.
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.

Topics of Interest

15.7 Other Applications A number of additional applications, not covered by the categories of system described in the preceding sections, are discussed in the following section. 15.7.1 Moving-map...

Chapter List Chapter 2: Coordinate Frames, Kinematics, and the Earth Chapter 3: The Kalman Filter This chapter provides the mathematical foundations for explaining the principles of navigation...

Overview This chapter presents two important modeling elements of an integrated navigation system: ellipsoid geometry. ellipsoid gravity. Like the different navigation frames presented in Chapter...

J. J. Spilker Jr., Stanford Telecom Sunnyvale, California 94089 [*] I Introduction The GPS satellite constellation is selected to satisfy many different conditions to provide worldwide...

9.4.3 Earth Models Inertial navigation and satellite navigation require models for the shape, gravity, and rotation of the earth. Navigation Coordinates Descriptions of the major coordinates...