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

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

1. Variation in scale of photograph can take place due variation in_____________
a) Datum
b) Azimuth
c) Zenith
d) Elevation

Explanation: The process of finding scale involves joining the points of equal elevation. If there is a change in joining the points then it might affect the scale produced. So, the variation of elevation points can cause variation in scale produced.

2. Which of the following indicates the formula for scale?
a) Ground distance / map distance
b) Map distance / ground distance
c) Map distance / elevation point
d) Elevation point / map distance

Explanation: A scale is a parameter which is assumed in order to reduce the points on the ground to the drawing sheet. For that the ground distance and the map distance must be known. So, the value of scale can be determined by dividing map distance to ground distance.

3. Scale at elevation point in photograph can be given as_____________
a) S = f/ (H – h)
b) S = f/ (H + h)
c) S = f/ (H * h)
d) S = f/ (- H + h)

Explanation: Joining of elevation points in a photograph is a crucial step which involves in the formation of scale of a photograph. Scale at elevation point can be given as, S = f/H-h. Where, f is the focal length, H is the height of the station, h is height from mean sea level.

4. Which of the following can also be used in order to determine the scale of a photograph?
a) Recurring fraction
b) Reciprocating fraction
c) Representation fraction
d) Reducing fraction

Explanation: Representation fraction is an expression which is used to determine the scale. It is simply the reciprocal of the scale value i.e., Rh = 1 / (H-h/f). The values of H, h, f are the same as that of the values in scale.

5. If all the ground points are projected vertically downward on the mean sea level, which scale is recommended to be used?
a) Datum scale
b) Average scale
c) Azimuth scale
d) Reference scale

Explanation: A datum scale can be used in case of photograph, as it is capable enough for determining the effective scale value. The use of this scale is possible only when the ground points are projected vertically downwards on mean sea level.
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6. The formula for average scale can be given as______________
a) S = f / (H+hav)
b) S = f / (H*hav)
c) S = f / (-H+hav)
d) S = f / (H-hav)

Explanation: Average scale is a conditional scale, which is appointed only when it meets the required condition. It can be applied only when the ground points are projected upward or downward on a plane. It is given as, S = f / (H-hav).

7. Which of the following indicates the right step for determination of scale?
a) Measuring ground distance
b) Comparing angles
c) Joining elevation points
d) Comparing zenith levels

Explanation: A scale can be determined by many factors. It involves many steps among the primary thing is to join the points of equal elevation. If this isn’t done then the scale parameter will be reduced to an unknown value, which can’t be used for drawing a map.

8. The value of horizontal distance can be determined by which of the following methods?
a) Traversing
b) Triangulation
c) Theodolite surveying
d) Compass surveying

Explanation: In order to determine the value of scale, the value of horizontal distance on the ground must be determined it can be given by the process of triangulation, as it involves quick output development.

9. Determine the scale at elevation point if the values of focal length, height of station and the height of mean sea level are given by 23cm, 76cm and 20cm.
a) 0.41cm
b) 0.4cm
c) 4.41cm
d) 1.41cm

Explanation: The scale at an elevation can be determined by
S = f/ (H – h). On substitution, we get
S = 23/ (76 – 20)
S = 0.41cm.

10. What will be the average elevation of terrain if the scale is given as 43m, focal length and height of the station as 4m and 20m?
a) 19.19 m
b) 91.91 m
c) 9.91 m
d) 9.9 m

Explanation: The average elevation of the terrain can be given as
S = f / (H-hav). On substitution, we get
43 = 4/ (20-hav)
hav = 19.91 m.

11. Photographic scale can be determined by using the photo distance.
a) True
b) False

Explanation: In case of a photograph, the value of scale can be determined by comparing the photo distance and the map distance which can be able to yield points of equal elevation and by joining them, scale can be determined.

12. For finding the scale of a photograph, the points must be equally elevated.
a) False
b) True

Explanation: Scale of photograph lies in joining the points of equal elevation and to know the horizontal distance on the photograph. By this, the scale can be determined by comparing ground length and photographic length.

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