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What is EDM in survey?

Electronic distance measurement in surveying

Electronic Distance Measurement

Electronic distance measurement (EDM) is a method of determining the length between two points using electromagnetic waves. EDM is commonly carried out with digital instruments called theodolites. EDM instruments are highly reliable and convenient pieces of surveying equipment and can be used to measure distances of up to 100 kilometers. Each piece of EDM equipment available at Engineer Supply provides dependably accurate distance measurements displayed on an easy-to-read digital screen. Devices known as total stations share similarities with theodolites and can be used to measure distances as well as angles.


A Theodolite is a instrument for measuring both horizontal and vertical angles, as used in triangulation networks. It is a tool used in the surveying and engineering industry, but theodolites have been adapted for other specialized purposes as well. A theodolite consists of a telescope mounted movably within two perpendicular axes, the horizontal or trunnion axis, and the vertical axis. When the telescope is pointed at a desired object, the angle of each of these axes can be measured with great precision, typically on the scale of arcseconds. The measurements are typically recorded by hand as they are not recorded by a computer or data collector.

Total Stations

A total station is an optical instrument used in modern surveying. It is a combination of an electronic theodolite (transit), an electronic distance measuring device (EDM) and software running on an external computer, such as a laptop or data collector.

Learn more about Transits, Theodolites, Total Stations, & levels

Many professionals depend on accurate measurements. Whether you are an engineer, surveyor, designer, architect, realtor, contractor, construction worker, estimator, or in another profession you know that you could lose business due to incorrect measurements. There are so many methods and tools available for measuring how do you know which tool to purchase for your measuring needs?

Read this brief guide on selecting the best measuring tool: How to measure almost anything

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