Leveling Equipment

a - Level

There are different types of Levels as follows,

1 - Dumpy Level

It is the type of Level in which whole body of level is cast in one unit.

2 - Tilting Level

Still being used, Level can be tilted in vertical plane with the help of tilting drum.

3 - Automatic Level

In this type the line of sight become horizontal when the Level is within certain limits. This system provides the works on the principal of gravitation.

b - Staff

It is the graduated rod of maximum 5m length usually available in telescopic form. The gradations are both in feets and meters. Smallest graduation in feet is 0.01 ft or 1/100 ft and smallest division in meters is .005m.

Technical Terms in Leveling

1 - Sights

A reading taken from a level on staff is called sight.

2 - Back Sight (B.S)

It is the first sight taken after setting of the instrument.

3 - Fore Sight (F.S)

It is the last sight taken before shifting the instrument.

4 - Intermediate Sight (I.S)

These are sights taken between F.S and B.S.

5 - Line of collimation

It is the straight line joining the intersection of cross hairs and optical center of object glass.

6 - Level line

It is the curved line equidistant from the center of earth at all points.

7 - Horizontal line

It is the straight line tangent to observer position. The of collimation obtained by a carefully leveled instrument is a horizontal line.

8 - Reduced level (R.L)

It is the level of a point with respect to a certain datum whose level is taken as zero.

9 - Datum

It is a certain reference level to which levels of all other points are referred

i.e in Pakistan Datum is mean sea level (MSL) at Karachi.

10 - Change point (C.P)

It is the last position of staff after which the instrument was shifted.

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