Abstract: In a ribbon suspended meridian gyroscope in which the gyroscope restoring moment is compensated by a compensating moment, which compensating moment is measured, a North reference angle is determined from a number of different measurements taken in various azimuthal positions. In order to shorten the total measurement time required, for each current individual measurement, the degree of accuracy required for this current individual measurement is determined from the measurement results of the previous measurements in accordance with the magnitude of the effects caused by an error of the individual measurement upon the error in determining the direction of North. The current individual measurement is then carried out to this degree of accuracy. In this manner, each individual measurement is only carried out to the degree of accuracy which corresponds to the weight of this individual measurement in the total error-budget for the North-determination for the respective North reference angle.

Abstract: A filter arrangement for generating an estimate of a measured variable influenced by disturbances, by means of a filter effecting a weighting of measuring signals characterized by means (50) for achieving a measure of the disturbance and means (52) for changing the weighting of the measuring signal in dependence on the measure of the disturbance. In this way, values of the measured variable which appear during the occurrence of the disturbance are not considered with the filtering or are considered with less weighting. In a tape-suspended restrained meridian gyro a characteristic oscillation of the system serves as the measure for the disturbance.