It consists of a telescope as an arrangement for sighting (similar to that present in the upper part of a theodolite). The telescope is fitted with a stadia diaphragm and can be used as tacheometer also for computations of horizontal distance and vertical elevations. The line of sight of the telescope is aligned along the fiducial edge. In this instrument, the object is sighted through the telescope and the distance is scaled off in that direction along the fiducial edge. Figure 33.3 shows a telescopic alidade.
Figure 33.3 Telescopic Alidade
The telescopic alidade is designed for greater precision and longer range of sights. It can be used with advantages for contouring and plotting of details during topographic surveying.