Abstract: A system for measuring the attitude of the platform that is movable relative to a fixed frame. The system comprises at least three platform mounting assemblies, each of the three mounting assemblies comprising (a) an isolation mount interconnecting the platform to the frame, the isolation mount permitting the platform to move relative to the frame, and (b) a means for measuring the movement of a point on the platform relative to the frame along three orthogonal axes. For each of the three mounting assemblies, the means for measuring, in the preferred embodiment, comprise a set of three linear position sensors having a known fixed attachment point to the frame and an end portion that terminates at or about the point on the platform. The linear position sensors or potentiometers generate measurement signals corresponding to the measurements of platform movement.