Consider, that in last century in technique and in technology in photogrammetry field big changes have taken place, it is good to know which one is better to use. One of the most significant parts of photogrammetry is making high-quality orthophoto mosaics. One of the important indicators of orthophoto mosaics is its geometrical quality which is affected by the accuracy of passing various steps in making orthophoto mosaics, such as aerial triangulation. If a photo is captured by a matrix sensor, it has two or three overlapping areas; in addition, the particular importance of the ground control points located in those areas for the accuracy of triangulation should not be overlooked. Generally, three overlapping areas are used for locating these points, but in specific cases, this does not work, and we have to use points located in two overlapping areas (e.g. areas covered by forest or water). In that case, it is necessary to know how it affects the accuracy of the whole aerial triangulation, the further processing of photos or the final product itself. The aim of the present research work is to investigate the geometrical quality of an orthophoto mosaic, using for that purpose two mosaics of the same area, made according to different principles of external aerial triangulation. This is the major aim of the present paper, mainly due to the fact that the authors are not aware of any previous research of the kind.