The authors consider one of the methods of simplified calibration, using a level three-meter leveling rod mounted horizontally as a removable test object. The calibration task is to determine the focal length of the camera and the field of photogrammetric distortion. The method is based on the assumption that the distortion is symmetrical and has a radial character. One shot is enough for calibration. Photography of the leveling rod is made from a distance, which allows when using this focusing the accommodation of the image in almost full volume within a single frame. The direction of the optical axis is perpendicular to the leveling rod. In the mathematical processing of the measurement results, the segments in the picture are summed, as well as the corresponding segments on the leveling rod. The ratio of these sums gives the scale of the plane, relative to which, distortion corrections can be calculated for each point of the image. For the same plane, using the distance to the leveling rod, the focal length of the image is calculated. The corrections for the angular points of the image are extrapolated. The techniques of shooting, the calculations of precision and tolerances of the shooting direction to the rod from the normal are described.