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Problem of missing entries in the field book

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Keywords: Levelling examples, levelling, rise and fall method, missing entries problem

Since we have already studied about levelling, now let’s move on to a specific problem in this section. The problem of missing entries in the field book is an application level problem, often asked in question papers. An example on this type of problem is illustrated as follows:

Problem: The following level readings have been taken from a page of a level book. Some of the readings are missing. It is required to fill all the entries in the page. Fill up the missing readings and apply the arithmetic checks.

Station BS IS FS Rise Fall RL Remarks
A 3.125           BM
B ×   × 1.325   125.505 TP
C   2.320     0.055    
D   ×       123.850  
E ×   2.655       TP
F 1.620   3.205   2.165   TP
G   3.625          
H     ×     123.090 BM

Solution:
The steps in the solution are as follows:

FS of station B= 3.125-1.325=1.800

BS of station B= 2.320-0.055=2.265

RL of BM= 125.505-1.325=124.180M

Fall of station E= 125.850-125.115=0.735

IS of station D = 2.655-0.735=1.920

BS of station E= 3.205-2.165=1.040

Rise of station H=123.090-120.945=2.145

FS of station H= 3.625-2.145=1.480

The missing entries are filled and presented in the following table:

Station BS IS FS Rise Fall RL Remarks
A 3.125         124.180 BM
B 2.265   1.800 1.325   125.505 TP
C   2.320     0.055 125.450  
D   1.920   0.400   123.850  
E 1.040   2.655   0.735 125.115 TP
F 1.620   3.205   2.165 122.950 TP
G   3.625     2.005 120.945  
H     1.480 2.145   123.090 BM
SUM 8.050   9.140 3.870 4.960    

Arithmetic checks:

ΣBS-ΣFS=8.050-9.140=-1.09

ΣRise-ΣFall=3.87-4.96=-1.09

LRL-FRL=123.09-124.180=-1.09

Since, ΣBS-ΣFS=LRL – FRL=ΣRise-ΣFall

Therefore, the calculations are correct.

 

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