Abstract: A surveying instrument and procedure are provided for the precise determination of elevation differences in the course of a surveying traverse. The instrument comprises an optical wedge 13 situated on the horizontal longitudinal line of sight axis 27 of the primary optical system between the objective lens 11 and a target under observation. The wedge is arranged for rotation about this axis and with such rotation angularly displaces the diverted line of sight 28 from the horizontal to the plane of the target. The degree of rotation required of the wedge to acquire the target 33 is measured by electro-optical angle encoder means 10, and the distance to the target by EDM means 24, 26. The difference in elevation is calculated trigonometrically by computer means utilizing as data the wedge diversion angle, the sine function of its rotation, the computed angular displacement of the line of sight, and the distance to the target.

Abstract: An improved mislevel sensing device having a balanced pair of capacitive pick-up circuits includes a pendulously-suspended common electrode assembly comprising a leaf spring member in the available flexing length of which is located a centrally-disposed hole which effectively reduces the cross-sectional dimensions of the suspension leaf member in that area, consequently restricting the beam-like flexure of the leaf to that area and away from sharp stress-imparting edges of leaf-clamping members of the device. The device further includes means for readily adjusting its attitude with respect to a primary reference axis of the host instrument, and means for providing protection of the functional capacitive couples from variable stray capacitive fields arising within the instrument, and from the intrusion of capacitance-effecting ambient moisture.