Surveying Questions and Answers – Curve Surveying – By Deflection Distances

This set of Surveying Multiple Choice Questions & Answers (MCQs) focuses on “Curve Surveying – By Deflection Distances”.

1. The method of deflection distances is used in which of the following cases?
b) Railway survey
c) Land survey
d) Town planning survey

Explanation: The deflection distances method is having at most priority in case of road surveys as the curvature for joining parallel straights is to be done without any error.

2. The method of producing offsets from the chords can also be named as ____________
a) Rankine’s method
b) Bisection of chords
c) Deflection distances
d) Two-theodolite method

Explanation: Deflection distances method is adopted in case of long curves, which generally implies in highways. Highway possess long curves which can’t be designed other than this method.

3. Which of the following indicates the formula used in deflection distances?
a) On = Cn + (Cn-1 + Cn)/2*R
b) On = Cn (Cn-1 + Cn)/2+R
c) On = Cn (Cn-1 – Cn)/2*R
d) On = Cn (Cn-1 + Cn)/2*R

Explanation: The formula for the offsets by chords produced include, On = Cn (Cn-1 + Cn)/2*R. the value of n depends upon the number of chords introduced and C represents chord length, where R is the radius of the curve.

4. Which of the following process can be adopted as an alternative of theodolite?
a) Bisection of chords
b) Deflection distances
c) Ordinates by long chords
d) Rankine’s method

Explanation: Theodolite usage is more in case of designing long curves. Long curve designation involves in lengthy calculation and developing number of chords, which can be done in deflection distances method. So, it can serve as an alternative.

5. Errors in deflection distances method are distributed to all the points.
a) True
b) False

Explanation: The occurrence of errors in all cases is common, but in case of deflection distances method the error can be distributed all over the points. If the error is more, then the curve should be re-set.
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6. Closing error can also be known as __________
a) Absolute error
b) Zero error
c) Subjecting error
d) Discrepancy

Explanation: Closing error occurs due to the mismatching of the beginning and the last points. It can be eradicated or reduced up to some extent based on the amount of error produced. It is also known as discrepancy.

7. While producing offsets by deflection distances method, the last offset must coincide with the beginning.
a) False
b) True

Explanation: The occurrence of closing error depends on the closing the curve due to offsets. If the beginning point doesn’t coincide with the end point, then closing error may occur which may lead to re-setting of the entire curve.

8. Determine the first offset if the chord length is given as 23.98m and the radius is given as 5.87m.
a) 84.98 m
b) 48.98 m
c) 48.89 m
d) 84.89 m

Explanation: The value of offset can be given as O = C2 / 2*R. On substitution, we get
O = 23.982 / 2*5.87
O = 48.98m.

9. Find the value of last offset, if the lengths of first and second chords are given as 45.87m and 62.87m with radius of curve 69.76m and length of chain being 30m.
a) 38.987 m
b) 83.987 m
c) 38.697 m
d) 83.697 m

Explanation: The value of offsets can be calculated by using,
On = Cn*(Cn – 1 + Cn) / 2*R, it can be simplified as
On = cꞌ*(C + cꞌ) / 2*R. On substitution, we get
On = 62.87*(30 + 62.87) / 69.76
On = 83.697m.

10. Find the value of chord length if the offset is given as 36.54m and the radius include 3.43m.
a) 15.38 m
b) 51.83 m
c) 15.83 m
d) 87.54 m

Explanation: From the deflection distances method, the value of chord length can be determined by
O = C2 / 2*R. On substitution, we get
36.54 = C2 / 2*3.43
C = 15.83m.

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