Abstract: For determining the interior shape of spherical tanks for the computation of the liquid volume of the same, the following steps are performed: An arbitrary system of coordinates is established based on field measurements in the tank of a given number of station points within the sphere. From the station points a plurality of reference points in the form of markers affixed to the inner surface of the sphere are identified with reference to said system of coordinates. In the field all the reference points and the inner surface of the sphere are photographed with double coverage for later representation of stereoscopic models in a photogrammetric autograph.All reference points are later plotted on a drawing sheet in a coordinatograph to establish a horizontal great circle plane of the sphere together with a first interim center of the sphere.