Surveying

Surveying has to do with the determination of the relative location of points on or near the surface of the earth. It is the art of measuring horizontal and vertical distances between terrestrial objects, of measuring angles between terrestrial lines, of determining the direction of lines, and of establishing points by predetermined angular and linear measurements.

Incidental to the actual measurements of surveying are mathematical calculations. Distances, angles, directions, locations, areas and volumes are thus determined from data of the survey. Also, much of the information of the survey is portrayed graphically by the construction of maps, profiles, cross-sections and diagrams.

Thus, the process of surveying may be divided into the field work of taking measurements and the office work of computing and drawing necessary to the purpose of the survey.

The earliest surveys known were for the purpose of establishing the boundaries of land, and such surveys are still the important work for many surveyors.

Every construction project of any magnitude is based to a greater or lesser degree upon measurements taken during the progress of a survey and is constructed about lines and points established by the surveyor.

P1 a n e s u r v e y i n g. That type of surveying in which the mean surface of the earth is considered a plane, or in which its spheroidal shape is neglected, is generally defined as plane surveying. With regard to horizontal distances and directions, a level line is considered as mathematically straight. The direction of the plumb line at any point within..the limits of the survey is considered as mathematically straight. The direction of the plumb line аt any point within the limits of.the survey is considered as parallel to the direction of the plumb line at any other point, and the angles of polygons are considered as plane angles.

By far the greater number of all surveys are of this type. Surveys for the location and construction of highways, railroads, canals are plane surveys, as are also the surveys made for the purpose of establishing boundaries, except state, provincial and national.

G e o d e t i c s u r v e y i n g. That type of surveying which takes into account the shape of the earth is defined as geodetic surveying. All surveys employing the principles of geodesy are of high precision and generally extend over large areas. Where the area involved is not great, as for a province, state, the required precision may be obtained by assuming that the earth is a perfect sphere. Where the area is large, as for a country, the true spheroidal shape of the earth is considered.

Дата добавления: 2015-07-19