Description and application for an automated inertial azimuth measuring system

Requirements for highly precise azimuth references for USAF weapons systems have led to an improved automated azimuth measuring system (AAMS). The AAMS represents the state-of-the-art for a highly accurate, automated, all-weather azimuth capability which can be used in either a laboratory or specialized field environment. The present system consists of two integrated inertial sensors, an angle transfer system, a tiltmeter array and a microprocessor. The inertial sensors use gimbal-mounted rate gyrocompasses to indicate the azimuths of two transfer mirrors with respect to true North. The azimuths are transferred to any number of reflectors by an autocollimator on a precision indexing table. Sight tubes carry low velocity air along each optical path. Highly sensitive tiltmeters are used to measure and correct for errors due to base motions of the inertial sensors. Data handling and functional operation are controlled by the microprocessor. The instrumentation was employed at a Minuteman missile engineering silo to monitor azimuthal motions of the missile. Recent results indicate a standard deviation of 2.1 arc seconds for a single observation. Proposed improvements include refined support electronics, improved measurements of tilts of the gyrocompasses, increased automation and more extensive software for signal processing.