# Technological Development and Application of Photo and Video Theodolites
## 2 Technological Development
### Development from 1981-1990  
Development during the 1980s placement emphasis on theodolite measurement systems (TMSs). ETs combined with integrated cameras, i.e., image CCD sensors, were used to measure spatial forward intersections using two or more instruments. The automatic aiming at fixed target points or projected laser spots was realized using image analysis techniques [8]. Most of these devices were used for industrial applications. In 1981, the Geodetic Institute of the University of Hannover took up the idea of using four-quadrant diodes as part of the Collaborative Research Center 149 within a subproject called \"automatic determination of the position of an object at sea using a tachymeter\". A semiconductor position-sensitive sensor built into the image plane of a tachymeter was used to detect the center of the light source located on a monitored ship. With the help of built-in servomotors, the instrument could monitor the ship, always keeping the light source in the middle of the field of view (FOV). This development was based on the AGA Geodimeter 700, which had infinite screws for fine adjustment, named GEOROBOT, and GEOROBOT II was later developed on the basis of the Geodimeter 710 instrument [27; 28]. Two instruments which marked this period were presented at almost the same time, i.e., Kern E2-SE (Figure 6, left) introduced in 1985 [29] and Wild TM-3000V (Figure 6, right) introduced shortly after [30]. These instruments were developed through projects from Kern and Wild and were actually called Kern SPACE and Wild ATMS during the project phase. The growing demands of manufacturers in the automotive and aerospace industries, who used theodolite measurement systems during assembly and quality control, were based on measuring spatial forward intersections using two or more instruments. To satisfy these demands, Kern and Wild integrated CCD image sensors and digital image acquisition into servomotorized theodolites. These so-called video theodolites had pan-focal telescopes, which means that the FOV changed as a function of distance to the target point. Kern E2-SE had a CCD image sensor with a resolution of 576 \(\times\) 684 px, and the image was recorded in the instrument's internal memory. It was the first video theodolite  
Figure 5: Contraves ECTS cinehedolite (**left**) [23], AGA-Minilir cinetheodolite (**middle**) [24], and Krupp Atlas Polarfix (**right**) [22]. in the world with the possibility of automatically aiming at a signaled target [2]. The CCD image sensor was used for autofocusing and for determining the target position relative to the optical axis of the telescope. The instrument had three integrated servomotors, two for horizontal and vertical axes and one for focusing, i.e., autofocus. The motors were designed to enable a positioning accuracy of up to \(\pm 0.1\)'' to be achieved, at speeds of up to \(54\)'' per second [31]. Once the autofocus was accomplished and the geometrical relationship between the target point and the instrument optical axis was determined using image processing algorithms, the instruments automatically drove the theodolite toward the target point and the measurements could be performed. A signaled target point realized by a projected laser point or a fixed marking was automatically aimed at by two or more corresponding instruments using image evaluation, allowing its 3D spatial coordinates to be determined [22]. Shortly after [PERSON], the Wild company introduced its video theodolite model TM3000V. The motorized video theodolite TM3000V was a further development of the precision theodolite T3000. In addition to the motors for the axes and the focusing lens, special elements of the motorized video theodolite were the camera and the processor integrated in the theodolite. Wild TM3000V had a CCD image sensor with a resolution of \(500\times 582\) px.