Abstract: Apparatus for measuring variation in scalefactor from a predetermined value for a vibrating structure gyroscope has a vibrating structure (R), fixed primary and fixed secondary drives (1, 13) for putting and maintaining the vibrating structure (R) in vibrating resonance, fixed primary and fixed secondary pick offs (2, 6) for detecting vibration of the vibrating structure (R), with the drives and pick offs (1, 13, 2, 6) being located radially around the vibrating structure (R), quadrature component and real component loop systems (7, 8), automatic gain control and phase locked loop systems (5, 22), a sin/cos pick off resolver (38) for receiving signals from the primary and secondary pick offs (2, 6) and for outputting signals to the quadrature component and real component loop systems (7, 8) and to the automatic gain control and phase locked loop systems (5, 22), a sin/cos drive resolver (37) for receiving output signals from the quadrature component and real component loop systems (7, 8) and from the automati