It is the branch of surveying which deals with any body of still or running water such as a lake, harbor, stream or river. Hydrographic surveys are used to define shore line and under water features. Hydro-graphic surveying are carried out for one or more of the following activities.

The survey of the shore line of a river is made by running a theodolite and tape traverse on a shore at a convenient distance form the edge of the water. If the river is narrow, a single theodolite and tape traverse is on one bank and both banks. Located by staid or plane table methods. If the river is wide, it is necessary to run traverses on both banks and locate each shore

In an extensive survey, the primary horizontal control is established primary horizontal control secondary once by running theodolite and tape traverse b/r the triangulation station, the traverse lines being run to following the shore lines approx. in survey of less extent the primer horizontal, control only is required and is established by running a theodolite and tape

Combination of two or more simple circular curves of different radius having their curvature in the same direction. Essentially, a compound curve consists of two curves that are joined at a point of tangency and are located on the same side of a common tangent. Though their radii are in the same direction, they are of different values. tr= perception/reaction time

Collimation error occurs when the collimation axis is not truly horizontal when the instrument is level. The effect is illustrated in the sketch below, where the collimation axis is tilted with respect to the horizontal by an angle a: