JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech IV REMOTE SENSING AND GIS Previous Question Paper (September - 2020 - R16)

The scale of a vertical aerial photograph is defined as the ratio of the distance on the photograph to the corresponding distance on the ground. For a vertical photograph taken with a camera of focal length f, the scale S is given by the ratio of the focal length to the flying height above the ground (H-h), where H is the flying height above sea level and h is the elevation of the terrain. Thus, S = f / (H-h). If the terrain is not level, the scale varies across the photograph.

Height measurement on a single vertical photograph is achieved using the principle of relief displacement. Relief displacement (d) is the shift in the position of an image point from the nadir due to the elevation (h) of the object above a reference datum. The relationship is expressed as d = (r * h) / H', where r is the radial distance from the principal point to the image of the top of the object, h is the height of the object, and H' is the flying height above the base of the object. By measuring the displacement d on the photograph, the height of the object can be calculated as h = (d * H') / r.

To calculate the height of the building, we use the relief displacement formula: h = (d * H') / r, where d is the relief displacement, H' is the flying height above the base of the building, and r is the radial distance to the top of the building.

1. Calculate the flying height above the base of the building (H'): H' = H - elevation of base = 11,400 ft - 1,400 ft = 10,000 ft.

2. Determine the relief displacement (d): d = distance to top - distance to base = 3.60 inches - 3.42 inches = 0.18 inches.

3. Identify the radial distance to the top (r): r = 3.60 inches.

4. Calculate the height (h): h = (0.18 inches * 10,000 ft) / 3.60 inches = 1,800 / 3.60 = 500 feet.

The height of the building is 500 feet.