What Is The Difference Between Differential And Profile Leveling .

upendra kumar

Differential Leveling

 Differential leveling

The differential leveling is the process used to determine a difference between two points.
The differential leveling is used where the points are a great distance apart.
The differential leveling is used where the difference of elevation between the points is large.
The differential leveling is used where there are obstacles between the points.
In the differential leveling to set up the leveling instrument several positions.

procedure

In the above picture to know the difference level between points A and B, here O1, O2, O3, and O4 are the level instrument station.
Set the level instrument at O1 and make a temporary adjustment and take the back site reading on A and also take fore site reading on C1.

H.I of O1= RL of A +staff reading on A= Height of instrument on O1
R.L of C1= Height of instrument on O1- Fore site staff reading on C1

H.I of O2= RL of C1 +B.S reading on C1= Height of instrument on O2
R.L of C2= Height of instrument on O2- Fore site staff reading on C2

H.I of O3= RL of C2 +B.S reading on C2= Height of instrument on O3
R.L of C3= Height of instrument on O3- Fore site staff reading on C3

H.I of O4= RL of C3 +B.S reading on C3= Height of instrument on O4
R.L of B= Height of instrument on O4- Fore site staff reading on B

Find the difference of level between A and B
= R.L of B - R.L of A
If the difference is positive then the A is lower than B.
If the difference is negative A is higher than B.

If the differential leveling is used for establishing the benchmark on B. Then used the same process closing the leveling on A. If the intermediate side if taken should be written in the I.S column in level book.
EXAMPLE OF LEVEL BOOK AND LEVEL CALCULATION

 POINT B.S I.S F.S H.I R.L REMARK B.M 1.255 101.255 100.000 A 1.750 99.505 B 2.150 2.750 100.655 98.505 C 1.950 98.750 D 1.550 99.105

PROFILE LEVELING

The main object of the longitudinal leveling or profile is to determine the undulation of the ground surface along the predetermined line at regular intervals.

It is used in the centerline of the road, railway, pipeline, canal, curve setting, finding the gradient of the proposed road. It is consist of a series of the single line in chaining direction.
It is used in the estimation of earthwork in the civil project.
Procedure:-
Image of centerline
The   ABC be the centerline of the road. Mark the points on the ground at required intervals Establish the two T.B.M near the A and the B side to check works. Set the instrument right side of the line AB and make carefully temporary adjustment Kept The staff is vertical on T.B.M nearly A. Read and book first staff reading as a backside reading and book in backside column in level book. Take the staff reading on the marked points on the ground. Booked the Staff reading as the intermediate side in the level book. According to the nature of the ground change point (C.P) make both sides of Centreline and booked in the level book as a foresight. set the instrument on L2 and L3 both sides of Centreline. After completing the take reading. Work should be closed on nearest theT.B.M
for check purposes. The following points should be born in mind at the leveling.
1. The back sight and fore side distance should be equal approximately.
2. The position of important features, such as nalla, river, road, etc should locate their actual dimension.