Surveying
the act or art of determining the boundaries, form, area, position, contour, etc., of any portion of the earth's surface, tract of country, coast, etc., by means of measurements taken on the spot; the art of determining the form, area, surface, contour, etc., of any portion of the earth's surface, and delineating it accurately on a map or plan. Land surveying is the art of applying the principles of geometry and trigonometry to the measurement of land. The principal operations are laying down or driving base lines and triangles on either side of the base. In large surveys it is desirable to lay down these triangles by measuring each angle with an instrument called the THEODOLITE (q. v.)., by which the accuracy of the measurement of the sides may be checked. Geodesic surveying comprises all the operations SUSA of surveying carried on under the supposition that earth is spheroidal. It embraces marine surveying.
Marine or hydrographical surveying ascertains the forms of coast lines, harbors, etc., and of objects on the shore, the entrances to harbors, channels, their depth, width, etc., the position of shoals, the depth of water thereon. Mining surveying may be either for the purpose of determining the situation and position of the shafts, galleries, and other underground excavations of a mine already in existence; or it may be for determining the proper positions for the shafts, galleries, etc., of a mine not yet opened. Railway surveying is a comprehensive term, embracing surveys intended to ascertain the best line of communication between two given points; it also includes all surveys for the construction of aqueducts for the supply of water to towns, etc. Topographical surveying embraces all the operations incident to finding the contour of a portion of the earth's surface, and the various methods of representing it upon a plane surface.
When only a general topographical map of a country is wanted, it is, in general, sufficient to survey the country with reference to its fields, roads, rivers, etc.