Using photo images to determine the geometric parameters of large objects

There is a huge class of structures in modern industrial and urban planning practice, the control of geometrical dimensions of which is very important. At the same time this process is extremely difficult for several reasons: inaccessibility, danger of being close to the structure during its operation, etc. For instance, such structures are the following: ship hull structures, radar antennas, high-rise buildings, towers, chimneys, cooling towers and many others. Traditionally, the geometry control of objects including the ones mentioned above was carried out by measuring by a ruler and comparing the measurements with drawings. In terms of modern production, this method has a number of significant drawbacks, such as low accuracy, long duration of measurements, direct contact with the object, etc., although it is often used due to its cheapness. However, in the overwhelming majority of cases, contact with such structures is either difficult or impossible. The paper describes the processing of photo images in order to determine the geometric parameters of large and inaccessible objects. It considers possible ways of forming reference lines on photo images. The technology for determining the roll of high-rise buildings such as chimneys based on their photo images is presented. We also describe some results of an experimental study of the influence of the location of the reference line relative to the axis of the chimney on the accuracy of determining its roll using the photographic method.