# Surveying Questions and Answers – Triangulation – Reconnaissance

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This set of Surveying Multiple Choice Questions & Answers (MCQs) focuses on “Triangulation – Reconnaissance”.

1. In the process of reconnaissance, map reference is taken.
a) True
b) False

Explanation: The Reconnaissance is process can be done with the help of existing maps. If they aren’t available, a preliminary Reconnaissance is done for allocating the general location of triangulation for that terrain.

2. Which of the following is not necessary for Reconnaissance process?
a) Sextant
b) Theodolite
c) Chain
d) Aneroid Barometer

Explanation: The usage chain might make the entire process a little bit tedious, so a steel tape is in that place. Theodolite, sextant are used for taking angles, Aneroid barometer for measuring elevations.

3. Height of the instrument depends upon __________
a) Elevation differences
b) Type of terrain present
c) Type of instrument used
d) Distance between stations

Explanation: The height of the instrument and the signal in the process of Reconnaissance depends upon the profile of the ground, distance between the stations, and relative elevations of stations.
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4. Height of the station above datum is given as __________
a) $$h = \frac{D^2 (1-2m)}{2R}$$
b) $$h = \frac{D^2 (1-2m)}{2}$$
c) $$h = \frac{D^2 (1+2m)}{2R}$$
d) $$h = \frac{D(1-2m)}{2R}$$

Explanation: Due to the absence of any obstruction on the ground, the value of the height of station is given as $$h = \frac{D^2 (1-2m)}{2R}$$ where D is the distance to the horizon, m is the mean coefficient of refraction and R is the mean radius of the earth.

5. In the process of Reconnaissance, which of the following is determined?
a) Slope
b) Elevation
d) Distance between stations

Explanation: In Reconnaissance, the elevation and the peak points in terrain are determined. These are compared with the proposed elevations to ascertain whether the line of sight is clear or not.

6. Reconnaissance process will give best output only on elevated grounds.
a) False
b) True

Explanation: Reconnaissance is a process which helps on determining the elevations in terrain and also the peak points in the terrain which help in determining slope which is a secondary thing.

7. While calculating h2 with reference to h1, line of sight must be ______ m above the point of tangency.
a) 5-6 m
b) 4-5 m
c) 3-4 m
d) 2-3 m

Explanation: The elevation of a station can be determined by $$h = \frac{D^2 (1-2m)}{2R}$$ and from taking its reference h2 will be calculated. It requires certain parameters like keeping the line of sight at a height of 2-3 m above the point of tangency.

8. For proper identification, station marks are marked with___________
a) Wood
b) Plastic
c) Copper
d) Concrete

Explanation: The marks of triangulation must be permanently marked with copper so as to make them visible all over the years. A minimum of two or three marks must be noted for easy identification.

9. Besides theodolite which among the following is used for taking angles.
a) Compass
b) Only theodolite
c) Total station
d) Sextant

Explanation: Compass is used only for determining bearings not for angles. Though theodolite is used, it sometimes might not be possible for setting the instrument. In that case, a sextant is used.

10. Determine the height of the station if the distance between the visible horizon is 44km.
a) 121.54m
b) 211.54m
c) 121.45m
d) 211.45m

Explanation: The height of the station can be determined by,
h = D2*(1-2m) / 2*R. here, m= 0.07, radius of earth = 6370km. On substitution, we get
h = 442*(1-2*0.07) / 2*6370
h = 121.54m.

11. Find the distance between the visible horizon, if the height of the station is given as 2.98m.
a) 8.66m
b) 6.88m
c) 8.68m
d) 2.86m

Explanation: The distance between the visible horizon can be given by,
$$D = \sqrt{\frac{h}{0.06278}}$$. On substitution, we get
$$D = \sqrt{\frac{2.98}{0.06278}}$$ D = 6.88m.

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