Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE) PDF Download

Surveying (Part 12)

Two cases may arise 

(I) An observation is made on the bright portion
(II) An observation is made on the bright line

(I) When the observation is made on the bright portion
b = Phase correction angel COP

Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)
Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)
Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)

 Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)
Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)
Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)

where r = radius of the signal b = angle between sun and the line OP

II. When the observation is made on the Bright line Ð SCO = 180 (q -b)

 Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)

Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)
Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)
Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)
Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)
Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)
Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)

 The phase correction is applied algebrically to the observed angle according to the relative positions of the sun and the signal, i.e., it is the +ve and zero.
Measurement of Base line The accuracy of any order of triangulation depends upon the accuracy of the measurement of its base line.
Hence in triangulation a base line is of prime importance.

Selection of the site for a Base line
1. The ground of the sight should be fairly level or uniformal.

Number of zeros: To eliminate the error due to inaccurate graduatios of the horizontal circle, the measures of the horizontal angles are taken in two or three different zones, i.e.,

Type of  Triangulations stations 

(i) Main station
(ii) Subsidiary stations
(iii) Satellite stations or Eccentric or false stations
(iv) Pivot stations

Signals and Towers
(a) Luminous signal, and
(b) Opaque signals or non-luminous signal

  • Base line is measurred by standard tape and after that following connections are applied to the measured base length.
    (1) Correction for standard length

Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE) Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)

where L = measured length of the line
l = designed length of the tape
C= correction fro absolute length
C = correction to be applied to the tape.

The sign of the correction Ca will be the same as that of C.

(2) Correction of Alignment

Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)

Cn = (l1+l2) - (l1 cos q1 + l2 cos q2) = l1 (1– cos q1)+l2 (1–cosq2).

It is always substractive If A and B are not intervisible, then

 Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)

(3) Correction for shope Cs = L – D

= L – (L2–b2)1/2

  Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)It is always substractive

or Slope correction = L–L cos q = L (1– cosq)

 Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)

4) Correction for Tension :

 Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE)

where,P= standard pull P = Pull applied during measurement

If applied pull in more, tension correction is + ve, and if it is less, tension correction is ‘–’ ve

The document Triangulations Stations | Civil Engineering SSC JE (Technical) - Civil Engineering (CE) is a part of the Civil Engineering (CE) Course Civil Engineering SSC JE (Technical).
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FAQs on Triangulations Stations - Civil Engineering SSC JE (Technical) - Civil Engineering (CE)

1. What is a triangulation station in civil engineering?
Ans. A triangulation station in civil engineering is a fixed point on the ground that is used as a reference for surveying and mapping. It serves as a starting point for establishing other survey control points and helps in accurately measuring distances and angles between different locations.
2. How are triangulation stations established in civil engineering?
Ans. Triangulation stations in civil engineering are established by using a network of interconnected triangles. Surveyors measure the angles and distances between these stations to create a network of reference points. The positions of these stations are then determined by mathematical calculations based on the measured data.
3. What is the significance of triangulation stations in civil engineering?
Ans. Triangulation stations are crucial in civil engineering as they provide a reliable and consistent reference for surveying and mapping. They help ensure accurate and precise measurements, which are essential for various engineering projects such as construction, infrastructure development, and land surveying.
4. Can triangulation stations be used for vertical measurements in civil engineering?
Ans. No, triangulation stations are primarily used for horizontal measurements in civil engineering. They help establish the positions of points on the ground relative to each other. Vertical measurements, on the other hand, are typically achieved using other techniques such as spirit leveling or GPS-based methods.
5. How can triangulation stations be accessed or identified in civil engineering projects?
Ans. Triangulation stations are often marked with a physical monument or a benchmark that can be easily identified on-site. These monuments may include a metal plate, a concrete pillar, or a brass disk embedded in the ground. Surveyors can then use specialized equipment to locate and access these stations during their fieldwork.
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