Electronic Distance Measuring Instruments (EDMI) determine linear distance by transmitting modulated electromagnetic radiation (infrared or microwave) toward a reflector and analyzing the returned signal, using either the time-of-travel method (D = ΔtC/2) or the more practical phase-difference method (2D = Mλ + (Δφ/2π)λ), where the total distance combines an unknown integer number of full wavelengths M with a fractional wavelength derived from the measured phase shift. This belongs to the domain of surveying, specifically linear/electronic distance measurement, and extends the broader theory of using electromagnetic wave modulation (amplitude, frequency, and pulse/impulse modulation of a carrier wave) to encode a measuring signal for precise ranging. The fundamental measurement equation additionally incorporates two systematic correction terms — the instrument constant (K1) and the target/prism constant (K2) — which account for offsets between physical measurement reference points and the true optical path.
Electronic Distance Measuring Instruments (EDMI) determine linear distance by transmitting modulated electromagnetic radiation (infrared or microwave) toward a reflector and analyzing the returned si…