Young, George, jr, Baxter, Hubert Eugene, joint author · New York, The Macmillan Co. · leaf 283
Y [XIII, § 220 220. Topography. When it becomes necessary to describeaccurately a very irregular surface, such as a piece of land, linesof level are found very useful. A map on which lines of levelare shown is called a topographical map, or a contour map, andthe lines of level are usually spoken of… … Fig. 247 from the horizontal scale. Shorter intervals between thecontour lines give greater accuracy, but they involve morelabor, of course. The natural surface of the earth follows no geometrical law.Hence its lines of level are free-hand curves (§ 108). Butwhere land has been graded into formal…
Geometry, Descriptive
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