The article is devoted to description of the method of air object (AO) range finding by the passive single-position optoelectronic complex (OEC), and the formula applied to find the range is produced. As there are no markers and signs in the air space, an air object proper size is used as a gauging distance unit. Determination of AO angular position relative to the OEC is carried out by the indirect method based on the analysis of its two-dimensional image on the photodetecting matrix and collation of the obtained data with the data held in the database. Determination of AO image linear dimensions is also based on the indirect method of required data obtaining by means of AO image analysis and its collation with AO reference 3-D model.