Chain Surveying:
In plane surveying, we usually measure horizontal linear distances between two points and angles between two lines. A linear measurement of distance among two points on the earth's surface can be carried out by several methods depending upon the degree of accuracy and precision required.
Chain surveying is the easiest method of surveying in which only linear measurements are made in the field. It is appropriate for survey of smaller areas on open ground to obtain measurements for plotting exact description of boundaries of a piece of land or for taking simple details. The principle of chain surveying is to give a framework consisting of a number of linked triangles, as the triangle is the just easy figure which could be plotted from the lengths of its side measured in the field. The field to be surveyed is divided within a number of triangles and the sides of the triangle are measured in the field. To get good output in plotting, a framework should consist of triangles that are as nearly equilateral as probable. Preferably all the sides of a triangle should be nearly equivalent having every angle nearly 60o to ensure minimum distortion because of errors in measurements of sides and plotting.
Objectives
After studying this unit, you should be able to
- Recognize equipment and instruments used for chain surveying,
- Define the principles and procedures of chain surveying like fixing of survey stations, setting of offsets and ranging of survey lines,
- Elaborates the errors and obstacles in chain surveying, and
- Record a measurement in the field book.