Inertial navigation for the urban warrior

Individual soldier geolocation in situations such as urban warfare where loss of Global Positioning System (GPS) track can impact mission success has become a critical problem. Concepts such as RF 'time difference of arrival' and 'dead reckoning' techniques have not demonstrated their ability to support navigation reliably inside buildings on their own. Inertial navigation is the only technology that operates independence of external assets. The advent of micromechanical inertial sensor technology has resulting low-cost, very small, low-power navigation system capable of fitting in a soldier's boot. A miniature navigator consisting of three micromechanical gyroscope and accelerometer packages, including supporting application- specific integrated circuit chips, and capable of operating in support of such a mission has been developed. However, because of accelerometer and gyroscope drift, navigating inertially over long time periods using even the most precise and most expensive inertial senor available today remains close to impossible. Inertial augmentation techniques are therefore required, and the concept of personal inertial navigation systems aided by zero velocity updating of the accelerometers with each footfall has been examined and shown to be sufficient to determine the location of an individual soldier accurately within a large building complex after hours of operation. In addition to the accelerometer, updates of the gyro via zero attitude rate techniques is an additional means to further enhance the position accuracy, as well as to provide an attitude reference in support of soldier carried targeting sensors.