The document Time Concept, Remote Sensing, GIS, GPS and Photogrammetry Civil Engineering (CE) Notes | EduRev is a part of the Civil Engineering (CE) Course Topic wise GATE Past Year Papers for Civil Engineering.

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**Question 1: A camera with a focal length of 20 cm fitted in an aircraft is used for taking vertical aerial photographs of a terrain. The average elevation of the terrain is 1200 m above mean sea level (MSL). What is the height above MSL at which an aircraft must fly in order to get the aerial photographs at a scale of 1:8000? [2019 : 2 Marks, Set-ll](a) 3200 m(b) 2600 m(c) 3000 m(d) 2800 mAnswer: **(d)

Solution:

Given focal length = 20 cm

as we know scale of vertical photograph

its given as 1 : 8000

Scale = 1 : 7500

f = 15 cm

**Question 3: A square area (on the surface of the earth) with side 100 m and uniform height, appears as 1 cm ^{2} on a vertical aerial photograph. The topographic map shows that a contour of 650 m passes through the area. If focal length of the camera lens is 150 mm, the height from which the aerial photograph was taken, is [2018 : 2 Marks, Set-I] **

A =100 x 100 m

Area on photo, a = 1 cm

Scale 1 cm =100

f = 150 mm

h = 650 m

Scale

Relief displacement,

d

r

Relief displacement,

d

Relief displacement

Thematic Mapper sensor = 8

Band 1 - Blue

Band 2 - Green

Band 3 - Red

Band 4 - Near Infrared (NR)

Band 5 - Shortwave Infrared (SWIR)

Band 6 - Thermal

Band 7 - Shortwave Infrared (SWIR)

Band 8 - Panchromatic

Given: H = 700 m, h

Relief distance,

d = q - r

= 112.5 - 82.40

= 30.1 mm

âˆ´

[where h is height of tower]

â‡’

âˆ´ h = 120.4 mm

= 90Â° 40'E - 82Â°30'E = 8Â°10'

The longitude of the given place is more than the standard meridian. Hence the local mean time of the given place will be ahead of the standard time.

= 0 hours and 32 minutes and 0 seconds

= 0 hours and 0 minutes and 40 seconds

Time for a difference of 8Â°10' = 32 minutes and 40 seconds

Local mean time = standard time + 32 minutes and 40 seconds

= 6 hours and 30 minutes + 32 minutes and 40 seconds

= 7 hours 02 minutes and 40 seconds

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