Tacheometer

Part of speech: noun

Definitions

1. An optical surveying instrument used to measure distances and angles quickly by sighting a graduated staff through a telescope
2. A telescope-based device surveyors use to determine distances rapidly from the angle subtended by a marked rod
3. Instrument for rapid land surveying that calculates the range to a target from readings taken through its sighting telescope

Etymology: A tacheometer is a surveying instrument for measuring distances and angles quickly, and its name is built from two Greek roots. "Tachy" comes from the Greek "tachys", meaning swift or quick, and "meter" comes from "metron", meaning measure. The compound therefore describes a device for fast measurement, which is exactly what the instrument was designed to provide: it let a surveyor determine distances from readings taken through a telescope rather than by laboriously chaining or pacing out a line on the ground. The word is one of many English coinages built this way from classical parts, and it is a modern formation rather than something the ancient Greeks would have recognised. The same pattern produced "speedometer" in a different sense of measure, and "tachymeter" is an alternative spelling of the same term. Both spellings are in use, with "tachymeter" being the form that appears most often in technical writing.

Synonyms: tachymeter