Geodesy-Celestial Body Position

Question 1

1. Position of a celestial body can be determined by:
   a) Nadir
   b) Azimuth
   c) Zenith
   d) Co-ordinates

Answer 1

Answer: d
Explanation: Any particle can be determined the usage of co-ordinates. It is required to allocate certain co-ordinate system for the proper output. The allocation depends on the type of work employed.

Question 2

2. The angle between observer meridian and declination circle is given as
   a) Hour angle
   b) Azimuth
   c) Bearing
   d) Zenith

Answer 2

Answer: a
Explanation: An hour angle can be described as the angle between observer meridian and declination circle which passes through the body. It is always prescribed to measure it from westward.

Question 3

3. The imaginary sphere on which stars appear to lie is known as
   a) Cylindrical sphere
   b) spheroid
   c) Celestial sphere
   d) Zenithal sphere

Answer 3

Answer: c
Explanation: Celestial sphere is an assumption in which it is assumed that the stars lie on it. The radius of the sphere can be of any value that means it is varying. Because of the fact that the stars are far from us, we assume centre of earth as the centre of celestial sphere.

Question 4

4. The point above which the satellite or any celestial body lies is known as
   a) Zenith
   b) Nadir
   c) Visible horizon
   d) Latitude

Answer 4

Answer: b
Explanation: Nadir point can be described as a point above which the satellite or any celestial body lies. This term is generally used in case of satellite related discussion. Zenith is a point which is present above the celestial body.

Question 5

5. Which of the following doesn’t represent the co-ordinate system used in determining position of celestial body?
   a) Spherical co-ordinate system
   b) Horizon system
   c) Dependent system
   d) Independent system

Answer 5

Answer: a
Explanation: For determining the celestial body position, certain co-ordinates are assumed and those are given as horizon system, independent equatorial system, dependent equatorial system, celestial latitude and longitude system.

Question 6

6. The horizon system depends on which of the following?
   a) Visible horizon
   b) Nadir
   c) Zenith
   d) Observer’s position

Answer 6

Answer: d
Explanation: The horizon system depends on the observer’s position. The horizon acts as a plane of reference and the co-ordinates of a celestial body can be taken as azimuth and altitude.

Question 7

7. Zenith distance can be given as z =
   a) z = 900 + α
   b) z = 900 * α
   c) z = 900 – α
   d) z = 900 / α

Answer 7

Answer: c
Explanation: Zenith distance can be determined as the angular distance from body to point on upper portion of celestial body. It is given as z = 900 – α.

Question 8

8. Equatorial circle is used as a reference in an independent equatorial system.
   a) False
   b) True

Answer 8

Answer: b
Explanation: The independent system is used for the publication of stars ephemerides and also the position of the stars. For this it requires circle of references, which can be taken as equatorial circle and declination circle.

Question 9

9. All the co-ordinates in dependent system will depend on observer’s position.
   a) False
   b) True

Answer 9

Answer: a
Explanation: Dependent system has two co-ordinates; among them the second co-ordinate is independent on the observer’s position. And it will have a declination as its circle of reference.

Question 10

10. In the dependent equatorial system, first co-ordinate represents on _________ and second co-ordinate represents on ____________
    a) Nadir, zenith
    b) Zenith distance, hour angle
    c) Hour angle, declination
    d) Zenith, declination

Answer 10

Answer: c
Explanation: The dependent co-ordinate system contains two co-ordinates off which the first co-ordinate is depended on the observer’s position and second is independent of it. Here, the first co-ordinate represents hour angle and the second one represents declination.

Question 11

11. Determine the spherical excess, if the area of the triangle is given as 32sq. m with radius 65m.
    a) 1562.24 m
    b) 1526.24 m
    c) 1562.42 m
    d) 1652.24 m

Answer 11

Answer: a
Explanation: The value of spherical excess can be given by using the formula,
E = Δ / (R2sin 1ꞌꞌ). On substitution, we get
E = 32 / (652sin 1ꞌꞌ)
E = 1562.24 m.

Question 12

12. If the radius of sphere is given as 43m and the spherical excess as 186.54m, find the area of a spherical triangle.
    a) 6109.85 sq. m
    b) 6019.58 sq. m
    c) 6091.85 sq. m
    d) 6019.85 sq. m

Answer 12

Answer: d
Explanation: The area of the spherical triangle can be given by
A = πR2E / 180. On substitution, we get
A = π432186.54 / 180
A = 6019.85 sq. m.