# Surveying Questions and Answers – Hydrographic Survey – Introduction

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This set of Surveying Multiple Choice Questions & Answers (MCQs) focuses on “Hydrographic Survey – Introduction”.

1. Which of the following doesn’t describe the use of hydrographic surveying?
a) Laying an Alignment
b) Making underground investigations
d) Establishing mean sea level

Explanation: Hydrographic surveying can find its use in making nautical charts for navigation, making underground investigations for construction, establishing mean sea level, determining shore line etc.

2. The process of measuring depth below the water surface is called _______
a) Sounding
b) Chaining
c) Traversing
d) Compass traversing

Explanation: Sounding indicates the process of measuring depth below the water surface. It involves calculation of the time travel by the sound waves. This can reduce the manual power and can have an enhanced report.

3. Which among the following can be possessed by the horizontal control?
a) Chaining
b) Triangulation
c) Theodolite
d) Compass

Explanation: The horizontal and vertical control can possess either triangulation or a traverse. This is considered as the preliminary survey procedure as it can be done for second or third order triangulations which can be used as a main control.

4. Transit tape is used in case of small survey.
a) False
b) True

Explanation: In case of small scale surveys, the triangulation will be more than required and usage of tape is preferred over it. This can have an advantage in economic perspective and also in terms of obtaining result.

5. Gauge readings are obtained after_______________
a) Compass survey
b) Chaining
c) Sounding
d) Traversing

Explanation: After the completion of the sounding procedure, the next step involved is figuring gauge readings. Gauge reading is taken because of the continuous change in level of water, which might affect the result of the survey.

6. Which of the following doesn’t come under the category of shore line survey?
a) Delineation of shore line
b) Location of shore details
c) Determination of the low and high water lines
d) Sounding

Explanation: Shore line survey involves in the delineation of shore line, location of shore details and their prominent features and in the determination of the low and high water lines for spring tides.

7. Which among the following doesn’t indicate the purpose of sounding?
a) Volume measurements
c) Making sub-aqueous investigations
d) Measurement of area

Explanation: Sounding is conducted in order to make nautical charts for navigation, measurement of area which are subjected to scour and making sub-aqueous investigations which is needed to secure the information of construction.

8. What will be the salinity of the sea water if the temperature of the sea water is about 45˚C and the velocity of sound is given as 1678 m/s?
a) 314.62
b) 214.62
c) 134.62
d) 143.62

Explanation: From the relation, V = 1410 + 4.21*T – 0.037*T2 + 1.14*S. we can calculate the salinity content. On substitution, we get
1678 = 1410 + 4.21*45 – 0.037*452 + 1.14*S
S = 134.62.

9. Among the following, which is having more prominence while conducting sounding?
a) Labor
b) Signal
c) Sounding pole
d) Suitable climatic conditions

Explanation: Sounding involves in measuring the depth of water below the water surface, which requires certain equipments like, sounding boat, lead lines, fathometer, sounding machine, sounding pole.

10. What is length of the sounding rod or pole?
a) 7-8 m
b) 5-8 m
c) 10-18 m
d) 15-18 m

Explanation: Sounding rod or pole, which is used in case of sounding process, is having a length of 5-8 m with 5-8 cm diameter. They are suitable for shallow and quiet water areas, where the rod is visible for placing.

11. The velocity of sound in sea can be determined by ____________
a) Refraction
b) Reflection
c) Polarization
d) Sounding machine

Explanation: Sounding process involves certain machines, which record the velocity of the sound waves produced. The machine can be named as sounding machine, which was invented by Weddele.

12. Determine the velocity of the sound in sea water if the surface temperature can be given as 32˚C and the salinity is given as 2.43.
a) 1590.6 m/s
b) 1509.6 m/s
c) 5109.6 m/s
d) 1590.9 m/s

Explanation: The velocity of the sound in sea water can be determined by using the formula,
V = 1410 + 4.21*T – 0.037* T2 + 1.14*S. on substitution, we get
V = 1410 + 4.21*32 – 0.037*322 + 1.14*2.43
V = 1509.6 m/s.

13. Find the value of the surface temperature, if the velocity of the sound in sea water can be given as 2000 m/s and the salinity as 5.32.
a) 57˚C
b) 75˚C
c) 52˚C
d) 72˚C

Explanation: From the velocity of the sound of sea water relation, we can determine the surface temperature. The relation is given as V = 1410 + 4.21*T – 0.037*T2 + 1.14*S. on substitution, we get
2000 = 1410 + 4.21*T – 0.037*T2 + 1.14*5.32
T = 57˚C (approximately).

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