The type of EDM incorporated into modern total station instruments is commonly of the electro-optical type, using infrared and laser light as a carrier signal. Perhaps the biggest development of theodolites was its integration with an electronic distance-meter (EDM), which emerged around 1940 and became commercially available in the late 1960s. With time, several technological developments have been incorporated into theodolites thus, the accuracy of angle and distance determination has significantly increased. The accuracy of mechanically and optically measured distances is low and not appropriate for terrain characteristic point coordinate calculations. We can measure the distances mechanically (with chains and measuring tapes), optically (with optical distance-meters and interferometers), and electronically (with electro-optical distance-meters and electronic distance-meters (EDMs)). To determine the point positions in the coordinate system, in addition to angles, we must measure the distance between the instrument and the target. There are optical and electronic theodolites. Lastly, the authors conclude, according to the achieved results, that IATS can today be used for determination of quasi-static and dynamic displacements with small and high amplitudes.Ī theodolite is a geodetic instrument for measuring horizontal and vertical directions, i.e., angles in the horizontal and vertical plane. The procedure of conducting measurements with this kind of instrument, as well as the analysis of acquired data and achieved results, is elaborated. The application of modern video theodolites (i.e., IATS) is presented through several experimental studies that were performed. This paper describes the technological development of photo and video theodolites divided into phases according to the main innovations in their development. They can be implemented in geodetic monitoring systems, which are an integral part of engineering structural diagnosis, and they provide essential information about the current condition of the structure. With the development of theodolites, their application became much wider today, they can be used for structural and geo-monitoring, i.e., for the determination of static and dynamic displacements and deformations of civil engineering structures such as bridges, dams, wind turbines, and high buildings, as well as natural structures, such as mountain slopes. The latest development, called image-assisted total stations (IATS), is a theodolite which consists of a classic robotic total station (RTS) with integrated image sensors. Development started in 19th century, but only in the last 15 years has commercial application been achieved in the geodetic profession. Photo and video theodolites represent the advanced development of classic theodolites. Theodolites are fundamental geodetic measuring instruments for all practical geodetic tasks, as well as for experimental geodetic scientific purposes.

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