Basic Methods of Ranging between Two Points

Ranging
It is a process of establishing intermediate point on a start line between the terminal points or station.

Methods of Ranging

There are two method of ranging

• Direct ranging
• In-direct ranging

Direct Ranging:

This kind of ranging is in process when all points are visible. As shown in the figure.

In-Direct Ranging:

The ranging in which intermediate points are interpolated by reciprocal ranging or running an auxiliary line. Indirect ranging is done where end points are not visible and the ground is high. 

Let A and B be the two station with rising ground or a hill between them (Fig. Indirect Ranging, Case-I)

Let two chainmen with ranging rod take up point at M1 and P1 (Fig. Intermediate Points- M,P) as nearly in line as they can judge and such that chainmen at M1 can see both the ranging rods at measurement of distance P1 and B and the chainmen at P1 can see the ranging rod at M1 and A.

The two chainmen than proceed to line in each other alternately, the chainmen at P1 directs the chainmen at M1 to M2 in line with A, and then the chainmen at M2 directs the chainmen at P1 to P2 in line with B. By successively direction each other into line, their position will be change until finally they are both in the line AB exactly, (i.e. the four ranging rods A, M, P and B are in the same straight line) when they fix their ranging rod.

The Position of these ranging rods (M and P) serves as intermediate stations for ranging the line and enables the chainmen to measure in a straight line between A and B. this method may also be used in ranging a line across a hollow as illustrated in (fig. Indirect Ranging, Case-II)