Читать книгу Pedestrian Inertial Navigation with Self-Contained Aiding - Doruk Senkal, Andrei M. Shkel - Страница 19

Magnetometry and barometry are two commonly applied techniques that are used to improve the navigation accuracy. Magnetometry is one of the most ancient aiding techniques developed for navigation applications, where measurement of the Earth's magnetic field can provide information about the orientation of the system. Nowadays, not just the orientation, but also the location of the system can be obtained by measuring the anomalies of the Earth's magnetic field in the navigation of low‐earth‐orbiting spacecraft (altitude less than 1000 km), where the position of the spacecraft can be estimated with resolution on the order of 1 km. Barometry estimates the altitude of the system by measuring the atmospheric air pressure. It has been shown that low altitudes above sea level, the atmospheric pressure decreases approximately linearly as the altitude increases with a rate of about 12 Pa/m. A pressure measurement resolution of 1 Pa, or an altitude measurement accuracy of less than 0.1 m, can be achieved with the currently available commercial micro barometers [26].

Another way of implementing estimations of absolute position is through computer vision, where images of the environment are captured to extract information. One of the most popular implementations is called the Simultaneous Localization and Mapping (SLAM), where the localization and mapping of the environment is conducted simultaneously. As a result, no pre‐acquired database of the environment is needed. The sensors used for this application do not necessarily have to be cameras, LIght Detection And Ranging (LIDAR) and ultrasonic ranging can also be used. In either case, the system extracts some information about the environment as an aiding technique to improve the navigation accuracy.