Notes on the Fundamental Problems Involved in Determining True North by Gyroscopic Methods

摘要

By considering the basic principles which operate in any system using gyroscopes to determine the direction of True North, an assessment is made of the conditions which must be achieved if this direction is to be accurate to within a few minutes of arc. It is shown that even if the gyroscopes were perfect it would still take several minutes to make an accurate determination of North because of the extremely small rates of rotation which have to be measured. One of the main difficulties is due to movements of the base on which the gyros are mounted; hence the worst case is probably that of an aircraft carrier in rough sea, but a parked aircraft, exposed to gusty condition presents quite a difficult problem. The accuracy requirements for the gyros and accelerometers are discussed and the operation of a typical system which seeks True North automatically is analysed in some detail. (Author)