Theodolite Survey

Theodolite Survey 

a horizontal geodetic survey of the terrain, done by means of a theodolite, to produce a contour map. In a theodolite survey, as distinct from tachymetric and phototheodolite surveys, the elevation characteristics of the relief are not determined. The technique is usually used on level terrain, in population centers, at railroad junctions, and in built-up areas.

The stages of a theodolite survey are (1) preparatory work (familiarization with the area, designation and fixing of the high points of the theodolite traverse), (2) angular and linear measurements over the theodolite traverse, (3) survey of the details of the area, and (4) correlation of the theodolite traverse to the points of the geodetic control network. Maps based on a theodolite survey are drawn up indoors, rather than outdoors, as in plane-tabling. The theodolite traverse is a system of broken lines in which the angles are measured by means of a theodolite. The sides of the traverse are usually laid out in level, solid places that are convenient for measurement. The sides are 50–400 m long, and the angles of inclination are up to 5°. The high points of the angles of the theodolite traverse are fixed by temporary and permanent markers.

A detailed survey is made from the reference points and lines of the theodolite traverse, which is laid out between the reference points obtained from triangulation or traverses or takes the shape of closed polygons. The quality of a completed theodolite traverse is determined by comparing the actual errors (discrepancies) with permissible errors. The error of angular measurement in a theodolite traverse usually does not exceed 1’, and for the sides it is 1:2,000 of their length.

M. E. PEVZNER