PRINCIPLE OF COMPASS SURVEYING

PRINCIPLE OF COMPASS SURVEYING

  The principle of compass surveying is traversing, which involves a series of connected lines. The magnetic bearings of the lines are measured by surveyor compass and the distances od the lines are measured by chain or tape. Such survey does not require the formation of a network of triangles.

  Interior details are located by taking offsets from main survey lines. Sometime subsidiary lines may be taken for locating these details.

  Compass surveying is recommended when:

a). A large area to be surveyed,

b). The course of a river or coast line to be surveyed and

c). The area is crowded with many details and triangulation is not possible.

  Compass surveying is not recommended for areas where local attraction is suspected due to the presence magnetic substances like steel structure, iron ore deposit, electric cable conveying current, and so on.

 

TRAVERSING

  As already started in the last section, surveying which involves a series of connected lines is known as traversing. The sides of the traverse are known as ‘traverse legs’.

  In traversing, the lengths of the lines are measured by chain or tape and the directions are fixed by compass or theodolite or by forming angles with chain and tape.

 A traverse may be two types- closed and open.

Closed traverse: When a series of connected lines forms a closed circuit, i.e. when the finishing point coincides with starting point of a survey, it is called a ‘closed traverse’. Here ABCDEA represents a closed traverse (Fig. 9). Closed traverse is suitable for survey of ponds, forests, estates, etc.

Open traverse: When a sequence of connected lines extends along a general direction and dose not return to the starting point, it is known as ‘open traverse’ or ‘unclosed traverse’ Here ABCDE represents an open traverse (Fig. 10).

(Next Post on “METHODS OF TRAVERSING”.)