# Surveying Questions and Answers – Photogrammetric Surveying – Scale of a Tilted Photograph

This set of Surveying Multiple Choice Questions & Answers (MCQs) focuses on “Photogrammetric Surveying – Scale of a Tilted Photograph”.

1. Which of the following photographs may have a varying scale?
a) Datum photograph
b) Horizontal photograph
c) Vertical photograph
d) Tilted photograph

Explanation: Varying scale indicates joining points of unequal elevation, which means the ground is not flat. Mainly, tilted photographs can be taken with or without reliefs. If it is taken with relief, scale cannot be uniform.

2. Among the following, which must be known for determining scale in a tilted photograph?
a) Focal length
b) Datum height
c) Azimuth
d) Zenith

Explanation: A scale in tilted photograph can be known by having certain parameters. They include swing, tilt, focal length, flying height. By using these, the varying scale of tilted photograph can be determined.

3. The geometric process involved in the determination of scale for titled photograph is____________
a) Spherical
b) Cylindrical
c) Analytical
d) Co-ordinate

Explanation: For determining the scale of tilted photograph, assumption of certain cases is must. While calculating those cases, it is required to adopt one of the geometrical methods available. In this process, generally, analytical method is adopted along with directions.

4. Which of the following indicates the formula of scale for a tilted photograph?
a) sh = (f*sec t / mn*sin t) / (H-h)
b) sh = (f*sec t * mn*sin t) / (H-h)
c) sh = (f*sec t + mn*sin t) / (H-h)
d) sh = (f*sec t – mn*sin t) / (H-h)

Explanation: The scale of tilted photograph can be given as sh = (f*sec t – mn*sin t) / (H-h). Here, f is the focal length of the lens used, mn is the perpendicular erected, t is the angle measured, and H is the height of the station, h is the height of the mean sea level.

5. Which of the following is not recommended in case of determining the scale of a tilted photograph?
a) Axis
b) Focal length
c) Height of the point
d) Tilt

Explanation: The determination of the scale of a tilted photograph generally requires focal length, height of the point, tilt, height of flight etc. Each of these is required to be substituted in the formula of the scale of tilted photograph for obtaining the scale.
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6. Length of the line considered in case of determining scale of tilted photograph can be determined by ____________
a) $$L = \sqrt{(X_a+X_b)^2/(Y_a+Y_b)^2}$$
b) $$L = \sqrt{(X_a+X_b)^2+(Y_a+Y_b)^2}$$
c) $$L = \sqrt{(X_a+X_b)^2*(Y_a+Y_b)^2}$$
d) $$L = \sqrt{(X_a+X_b)^2-(Y_a+Y_b)^2}$$

Explanation: The length of the line established by using co-ordinates can be determined by using the formula,
$$L = \sqrt{(X_a+X_b)^2+(Y_a+Y_b)^2}$$. This is established by using the co-ordinates of the points taken while having their measurements.

7. Which of the following type of photograph can be used for the generation of maps?
a) Tilted photograph
b) Vertical photograph
c) Horizontal photograph
d) Datum photograph

Explanation: Generation of map requires a photograph with a uniform scale, which is quite simple in case of vertical photograph. So, it is most probably adopted. But, in the case of tilted photograph the scale is not uniform with consideration of relief. Because of this reason, a combination of vertical and tilted photographs is considered sometimes.

8. Determine the length of the line AB having co-ordinates (2, 4), (6, 7).
a) 3.16m
b) 31.6m
c) 13.6m
d) 13.9m

Explanation: The length of the line AB can be determined by using the formula,
$$L = \sqrt{(X_a+X_b)^2+(Y_a+Y_b)^2}$$. On substitution, we get
$$L = \sqrt{(2+6)^2+(4+7)^2 )}$$
L = 13.6m.

9. Flying height can be determined by using tilted photograph.
a) True
b) False

Explanation: Tilted photograph is used in the determination of flying height which ios placed exactly above the horizon. For this image of the two points and their elevations must be known for accessing any further.

10. For identification of length of a line, co-ordinates must be known.
a) True
b) False

Explanation: The establishment of co-ordinates must be needed in order to have a clear idea about the length of line needed. Co-ordinates are substituted in the length of the line determination formula for obtaining the length required.

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