Topography is that branch of surveying by which any portion of the land surface of the earth is mapped in plan on a specified scale or proportion of nature. With the plane-table such a map is constructed on the ground by at once drawing upon the paper, which is Spread upon the table, the angles subtended by different objects, and determining by intersections their relative positions, instead of reading off the angles on graduated instruments and afterward plotting the lines by means of a protractor, as is done in other methods of surveying. The practice with the plane-table has in this respect a great advantage in directness and precision. The measurement of distances and of vertical angles are used, in conjunction with the method of intersections, to obtain all the data for representing the horizontal and vertical features on the map, which is drawn in the field with pencil, the details being filled in according to established conventional signs.
The plane-table of the Coast Survey (see Sketch No. 30) is composed of a well-seasoned drawing-board, with beveled or rounded edges, about thirty inches in length, twenty-four in width, and three-quarters of an inch thick. It is commonly made of several pieces of white pine, tongued and grooved together, with the grain running in different directions to prevent warping. It is supported upon three strong brass arms, to which it is fastened by screws passing through4 treatise ON the plane-table.
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Publisher - Forgotten Books
Language - English
Author(s) - U. S. Coast and Geodetic Survey
Published Date - August 27 2019
ISBN - 9780364368947
Dimesions - 22.9 x 15.2 x 0.6 cm
Page Count - 42
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