(γῆ and διαίω I divide), that part of practical geometry which relates especially to the measurement and division of surfaces. In its more extended signification geodesy embraces all the trigonometrical and astronomical operations necessary for the construction of maps, for measuring the length of a terrestrial degree, &c.; and includes, in short, all those operations which relate to the measurement of the earth's surface. See Figure of the Earth, Geography, and Trigonometrical Survey.