When building phototriangulation ways to identify landmarks with gross blu nders in planning coordinates or their identification. They are based on an assessment of the condition of the equality the scale of line segments connecting the landmarks. However, in this case, there is the possibility of detecting a blunder in the situation of landmarks only in the direction of the segment. The article considers a method of detecting a blunder in the situation of landmarks also in the perpendicular direction to the cut. This assessed the condition of equal angles between identical segments. It is shown that as the scale and angles are invariants of orthogonal transformations, it is advisable to apply them as criteria to stage the planned reduction of phototriangulation. In the process of analysis of the quality of landmarks reveals the real level of error plane coordinate landmarks. This treatment begins with a task notoriously tough admission, which excludes high-quality landmarks. Then follows a gradual increase in the tolerance. As a criterion for task completion is assumed that the correct project build the mapping component of the anomalous landmarks should not exceed a certain level in the order of 10 - 15 percent. An example of the practical application of the method when building a phototriangulation for the images of TK-350, scale 1 : 650 000, obtained in runs KKK «Comet».