The North Finding Module

Abstract

Smiths Industries has developed a low-cost North Finding Module (NFM) for the U.S. Army Research Laboratory (ARL) and the U.S. Army Missile Command (MICOM). This paper provides a description of the system, details of the design, and performance results. The primary requirements of the NFM are to establish navigational heading relative to true north within 3 min statically and within 1 min dynamically from any initial heading with an error of less than 10 mrad. The system utilizes Smiths Industries dynamically tuned gyroscopes (DTGs), Allied Signal digital accelerometers, and the Collins precision low-cost GPS receiver (PLGR). An extensive system executive adapts the Kalman filter measurements for the current environment; i.e., all available measurements are optimally utilized in the presence of physical motion, the state of the GPS receiver, heading uncertainty, etc. Field test data on a prototype system show the static and dynamic performance of the NFM.