Definition, Importance and types of Surveying

Definition of Surveying

Surveying is defined as the science of making measurements of the earth specifically the surface of the earth. This is being carried out by finding the spatial location (relative / absolute) of points on or near the surface of the earth. Different methods and instruments are being used to facilitate the work of surveying. The primary aims of field surveying are : •  to measure the Horizontal Distance between points. •  to measure the Vertical elevation between points. •  to find out the Relative direction of lines by measuring horizontal angles with reference to any arbitrary direction and •  to find out Absolute direction by measuring horizontal angles with reference to a fixed direction. These parameters are utilized to find out the relative or absolute coordinates of a point / location. Importance of Surveying to Civil Engineers The planning and design of all Civil Engineering projects such as construction of highways, bridges, tunnels, dams etc are based upon surveying measurements. Moreover, during execution, project of any magnitude is constructed along the lines and points established by surveying. Thus, surveying is a basic requirement for all Civil Engineering projects. Other principal works in which surveying is primarily utilised are •  to fix the national and state boundaries; •  to chart coastlines, navigable streams and lakes; •  to establish control points; •  to execute hydrographic and oceanographic charting and mapping; and •  to prepare topographic map of land surface of the earth. Objectives of Surveying •  To collect field data; •  To prepare plan or map of the area surveyed; •  To analyse and to calculate the field parameters for setting out operation of actual engineering works. •  To set out field parameters at the site for further engineering works. Divisions of Surveying The approximate shape of the earth can best be defined as an oblate tri-axial ovaloid. But, most of the civil engineering works, concern only with a small portion of the earth which seems to be a plane surface. Thus, based upon the consideration of the shape of the earth, surveying is broadly divided into two types. Geodetic Surveying Plane Surveying Fundamental assumptions in Plane surveying •  All distances and directions are horizontal; •  The direction of the plumb line is same at all points within the limits of the survey; •  All angles (both horizontal and vertical) are plane angles; •  Elevations are with reference to a datum.