The Usage of Gyros in North Finding Systems

Abstract: As surprising as it may seem, accurate north finding, with an error of only several milli-radian, is still a very difficulttask and has been achieved only with very expensive systems. On the contrary, there are very simple systems that give theazimuth with an angular error five times superior but for a price a hundred times inferior. Moreover, these systems generally arenon-autonomous (i.e. they are environment dependent and can lose their precision in many situations). This assessment leads tothe following relevant question: Is it possible to design a north finding system with good precision, for a moderated cost and thatworks in any situation?This report presents and evaluates a solution which attempts to answer this problem. This solution is based on a gyrocompassingprinciple: a gyro measures the earth’s angular velocity in order to find the azimuth. This solution can be implementedfollowing several methods, this report presents and compares two of these implementations: Maytagging and Carouseling. Thecomparison is made thanks to a theoretical study, a computer simulation and tests on a real model designed for this report.Carouseling allows us, in theory, to reach an accurate azimuth, but puts mechanical constraints on the system. Maytaggingimplementation seems adapted considering trade-off between precision and cost. Further improvements on gyros will certainlymake systems based on gyro-compassing the most efficient autonomous systems for north finding.In this report, precisions reached by the different implementations are not made explicit for confidentiality reasons.