Abstract: An apparatus for determining the distance on the earth between (a) a point below an observation point at a known height, and (b) the base of an object of a known height. The apparatus includes a stadimeter having two pivots spaced from one another and two levers mounted for pivotal rotation with a mirror on each lever which face one another and are in parallel. An object height adjustment assembly is included which has a carriage with guide means and a member for movement perpendicular to the centerline of the guide and which member bears against the lever arm which tilts the lever arms upon movement of the member, the lever arms being biased into a normal position. Reference markings and a reader indicia are included.