PRINCIPLE OF ELECTRONIC DISTANCE MEASUREMENT
Electronic Distance Measurement (EDM) is a technology used for measuring the distance between two points using electromagnetic waves. The basic principle of EDM involves the transmission of an electromagnetic signal from a transmitter to a reflector placed at the target point, and then the reception of the reflected signal by a receiver at the measuring instrument.
The EDM instrument sends out a modulated electromagnetic wave that travels through the air and is reflected back from the reflector at the target point. The instrument then measures the time it takes for the wave to travel from the instrument to the reflector and back again. By multiplying the time taken by the speed of light, the distance between the instrument and the reflector can be calculated accurately.
There are different types of EDM instruments, including:
- Phase-based instruments: These instruments measure the phase difference between the transmitted and received signals. They are highly accurate and are commonly used in surveying and engineering applications.
- Time-based instruments: These instruments measure the time it takes for the signal to travel to the reflector and back again. They are less accurate than phase-based instruments but are still widely used in construction and building projects.
- Frequency-based instruments: These instruments use the Doppler effect to measure the frequency shift of the signal reflected from the reflector. They are commonly used in geodetic applications.
EDM instruments can be used for a variety of applications, including surveying, engineering, construction, and mapping. They are highly accurate and can measure distances up to several kilometers, depending on the type of instrument used. However, environmental factors such as atmospheric conditions can affect the accuracy of the measurements.
