Number of zeros: To eliminate the error due to inaccurate graduations of the horizontal circle, the measures of the horizontal angles are taken in two or three different zones, i.e., Face Ð 90º, Face L 180º Face L 270º.
Type of Triangulation stations
(i) Main station
(ii) Subsidiary stations
(iii) Satellite stations or Eccentric or false stations
(iv) Pivot stations
Signals and Towers The signals may be classified as
(a) Luminous signal, and
(b) Opaque signals or non-luminous signal
(1) Correction for standard length
where L = measured length of the line
l = designed length of the tape
Ca = correction for 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
Cn = (l1+l2) – (l1 cosq1 + l2 cos q2)
= l1 (1– cosq1)+ l2 (1- cosq2)
It is always substantial
If A and B are not intervisible, then
(3) Correction for slope
Cs = L – D = L – (L2 –b2)1/2
It is always substantial
or slope correction =L-L cos q = L (1-cos q)
DOAP, tan
0r
and
Where, r = radius of the signal q = angle between the sun and the line Op.
Resonance
Preliminary field inspection of the entire area to be concerned by triangulation is known as resonance.
It includes the following operations:
(i) Proper examination of the terrain
(ii) Selection of suitable position for baselines
(iii) Selection of suitable positions of triangulation stations.
(iv) Determination of intervisibility of triangulation stations.
Determination of intervisibility of stations If there is no obstruction due to intervening ground, the distance of visible horizon from the station of known elevation above mean sea level may be calculated with the formula. h = 0.06735 D2
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1. What is triangulation in civil engineering? |
2. How is triangulation used in civil engineering? |
3. What are the advantages of using triangulation in civil engineering? |
4. Are there any limitations or challenges associated with triangulation in civil engineering? |
5. What is the role of triangulation in land surveying? |
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