(1) Aerotriangulation using a mechanical, optical, or optomechanical model of the relationship between image point and object point. Two principal methods are used: the radial method, which obtains only the horizontal coordinates of the ground points; and stereotriangulation, which uses a stereoscopic plotting instrument to obtain horizontal coordinates, vertical coordinates or both. (2) The process of determining the location and orientation of the aerial camera at the times the photographs were taken. This meaning is rare.