How to find R.L

 There are two methods of find R.L.:-

(1) Height of Instrument Method OR Line of Collimation method

(2) Raise or Fall method.

First we will learn about Height of instrument method :-

This is the Table for find R.L.:-

Ch.	B.S	I.S	F.S	H.I	R.L	Remark
0+000	1.135			101.135	100
0+010		1.543			99.592
0+020		1.238			99.897
0+030	2.034		0.964	102.205	100.171	CP1
0+040		1.342			100.863
0+050		2.460			99.745
0+060			1.239		100.966	End Point

 

Check formula :-  

∑ B.S -∑F.S = Last R.L. - First R.L.

 

PROCEDURE:-

(1) First of all we have an given R.L which is known as T.B.M.

(2) After this we have to set the machine and level it.

(3) Then, the staff has put on the given T.B.M. then notes the reading with cross hair.

(4) This reading note in the B.S column.

(5) This reading plus we have been R.L to what we have been given then we found H.I.

 

Ch.	B.S	I.S	F.S	H.I	R.L	Remark
	1.135			101.135	100

 

R.L +B.S = H.I

100 +1.135 = 101.135

 

(6) Now our machine is completely set.

(7) Then staff will change another chainage point and read reading now this time reading will note in I.S column.

Ch.	B.S	I.S	F.S	H.I	R.L	Remark
0+000	1.135			101.135	100
0+010		1.543			99.592

 

(8) To find R.L, I.S is minus with H.I. Then we got R.L of that point.

(9) Now, staff should be take another point to find R.L of that point After putting the staff note down the reading. again it is minus in the H.I.

 

Ch.	B.S	I.S	F.S	H.I	R.L	Remark
0+000	1.135			101.135	100
0+010		1.543			99.592
0+020		1.238			99.897

 

(10)  101.135-1.238 = 99.897 R.L of any point should be write in front of that chainage point.

 

(11) Suppose this is our last point, after this, if we have to shift the machine, then we will write this point on F.S column.

 

(12) Again we minus that reading on H.I. to R.L.

 

Ch.	B.S	I.S	F.S	H.I	R.L	Remark
0+000	1.135			101.135	100
0+010		1.543			99.592
0+020		1.238			99.897
0+030			0.964		100.171

 

(13) After this we have to shift the machine and keep the staff in the same place.

(14) After setting the instrument we take  the reading and write on the B.S. column. This B.S Reading write in front of Last reading taken in F.S then plus the old R.L to get new H.I

(15)

 

Ch.	B.S	I.S	F.S	H.I	R.L	Remark
0+000	1.135			101.135	100
0+010		1.543			99.592
0+020		1.238			99.897
0+030	2.034		0.964	102.205	100.171	CP1

 

(16) This is plus to find new H.I. After this we take another reading to find R.L of that point.

 

(17) Again this reading is note down the I.S and minus the new H.I to find R.L.

 

 

Ch.	B.S	I.S	F.S	H.I	R.L	Remark
0+000	1.135			101.135	100
0+010		1.543			99.592
0+020		1.238			99.897
0+030	2.034		0.964	102.205	100.171	CP1
0+040		1.342			100.863

 

(17) The whole procedure repeated until the R.L of all points are not found.

 

We done the all point we should check that it is write or wrong

to check this there is a formula which is known as check formula:-

 

Check formula :-  

∑ B.S -∑F.S = Last R.L. - First R.L.

 

To check all the B.S are Plus and All the F.S. then minus. then last R.L is minus with first R.L.

 

Like that :-

 Sum of B.S =1.135+2.034= 3.169

 Sum of F.S =0.964+1.239=2.203

       after subtract we get= 0.966

then minus last R.L =100.966 minus First R.L =100

we get= 0.966

Which is correct.

then we do correct level