ABSTRACT
The introduction of electronic distance measurers (EDMs) into surveying practice became a real technical revolution. Early EDMs could only provide the required precision and distance range through the use of optical reflectors. Contemporary surveying EDMs employ semiconductor-based lasers as their light source. These lasers have a high coefficient of performance, narrow-band spectrum emissions, and project luminescent body of only a few microns in size. Two types of semiconductor lasers are primarily used. The main element of an EDM is its optical detector. The main block of an EDM is the timer that measures discrete intervals with very high accuracy. Most pulse EDMs have pulse amplitude stabilizers where the pulse packet is integrated. These stabilizers have different outputs actuating the device, however their input devices are based on the same principle. An actuating device is a reverse electric motor including a gear reducer with an optical attenuator on its axis.
