The aim of this paper is to present methods of estimating and guidelines for verifying the accuracy of optical photogrammetric measuring systems, using for measurement of large size elements. Measuring systems applied to measure workpieces of a large size which often reach more than 10000mm require use of appropriate standards. Those standards provided by the manufacturer of photogrammetric systems are certified and are inspected annually. To make sure that these systems work properly there was developed a special standard VDI / VDE 2634, "Optical 3D measuring systems. Imaging systems with point - by - point probing. " According to recommendations described in this standard research on accuracy of photogrametric measuring system was conducted using K class gauge blocks dedicated to calibrate and test accuracy of classic CMMs. The paper presents results of research of estimation the actual error of indication for size measurement MPEE for photogrammetric coordinate measuring system TRITOP.