Surveying (Part - 8) Civil Engineering (CE) Notes | EduRev

Civil Engineering SSC JE (Technical)

Civil Engineering (CE) : Surveying (Part - 8) Civil Engineering (CE) Notes | EduRev

The document Surveying (Part - 8) Civil Engineering (CE) Notes | EduRev is a part of the Civil Engineering (CE) Course Civil Engineering SSC JE (Technical).
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Surveying (Part 8)

Tangential Method of Tacheometry: In tangential Tacheometery, horizontal and vertical distance from the instrument to the staff position, are computed from the observed vertical angle of two targets fixed at a known distance S on the staff.

DEPENDING UPON THE VERTICAL ANGLES, THREE CASE MAY BE ARISE :

1. Both vertical angles may be elevation angles.
2. Both vertical angle may be depression angles.
3. One of the angle may be an elevation angle and the other may be a depression angle.

Case 1 : Distance and elevation angle :

 Surveying (Part - 8) Civil Engineering (CE) Notes | EduRev

Let A and B represent two targets fixed S metres apart on a staff held vertical at D.
Let O represent the trunnion axis of the theodolite.

 Surveying (Part - 8) Civil Engineering (CE) Notes | EduRev

þ V = D tan a2

Surveying (Part - 8) Civil Engineering (CE) Notes | EduRev

þ V - S = D tan a1

Substracting equation (ii) from equation (i), we get S = D (tan a2 – tan a1)

 Surveying (Part - 8) Civil Engineering (CE) Notes | EduRev
Surveying (Part - 8) Civil Engineering (CE) Notes | EduRev

CASE 2. Distance and depression angle

Surveying (Part - 8) Civil Engineering (CE) Notes | EduRev þ  V = D tana 2

  Surveying (Part - 8) Civil Engineering (CE) Notes | EduRev  þ V - S = D tana 1

Substracting equation (ii) from equation (i), we get

S = D (tan a2– tana1)

 Surveying (Part - 8) Civil Engineering (CE) Notes | EduRev
Surveying (Part - 8) Civil Engineering (CE) Notes | EduRev

Note : The most common method of tacheometry is a fixed hair stadia method, using a staff held vertically.
 

THE SUBSTANCE BAR : The substance bar is an instrument usd for measuring horizontal distances in the area where direct chaining becomes difficult due to undulations or other obstructions.
Comput

 Surveying (Part - 8) Civil Engineering (CE) Notes | EduRev
Surveying (Part - 8) Civil Engineering (CE) Notes | EduRev(where a is very small) 

Surveying (Part - 8) Civil Engineering (CE) Notes | EduRev(where a is very small) 

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