Also tachyomoter. [mod. f. Gr. ταχύ-ς swift + -METER; so F. tachymètre (a form more on Gr. analogies than TACHEOMETER).] Name of a surveying instrument, adapted to the rapid location of points on a survey. So Tachymetric a., Tachymetry, the use of such an instrument.
1860. Mayne, Expos. Lex., Tachymeter, term for an instrument for quickly measuring level surfaces.
1891. Buff & Berger, Handbk. Engin. & Surv. Instr., 109. The name Tachymeter, or rapid measurer, has been applied for many years, in Europe, to instruments of this description. Ibid. Tachymetry.
1900. H. M. Wilson, Topogr. Surveying, xii. 236. Tachymetry, or, as it is sometimes called, tachyometry … enables the operator, by a single observation upon a rod, to obtain the necessary horizontal and vertical data for the determination of the three elements of position of a point on the surface of the earth. Ibid. There are practically two systems of tachymetric measurement: The angular or tangential system; and The stadia, telemeter, or subtend system. Ibid., xiii. 282. A most satisfactory tachymeter, both for filling in details on large-scale maps, and for carrying on rough geographic or exploratory surveys.
