Low-altitude aerial photographs, Length of Curve and Long cord

In multilevel classification system, Level IV classification is suitable for

• (a) Landsat MSS images
  
• (b) High-altitude aerial photographs
• (c) Low-altitude aerial photographs
  
• (d) Medium-altitude aerial photographs
  

(C) LOW-ALTITUDE AERIAL PHOTOGRAPH

LEVEL	SYSTEM	IMAGE SCALE
I	Landsat TM and MSS images; AVHRR images	Smaller than 1:250,000
II	High-altitude aerial photographs; TM  and SPOT images AVHRR images (with ancilliary data)	1:80,000 to 1:250, 000
III	Medium-altitude aerial photographs	1:20,000 to 1:80, 000
IV	Low-altitude aerial photographs	Larger than 1:20,000

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Directions for the following  (02) items:

Read the following information and answer the two items that follow:The chainage of the intersection point of two straights is 1060 m, and the angle of intersection is 120°.  If radius of a circular curve to be set out is 570 m, and peg interval Is 30 m.

What is the length of the curve?

• (a) 190π m
  
• (b) 185π m
• (c) 180π m
• (d) 170π m
  

(A) 190π m
Length of curve = Angle subtended at O × Radius
L = π/3 × 570 = = 190π m

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What is the length of the long chord?

• (a) 370 m
  
• (b) 470 m
• (c) 670 m
• (d) 570 m
  

(D) 570 m
Length of long chord = AB  =2Rsin (∆/2) = 2Rsin (60/2) =2Rsin (30)
2×R×1/2   = 2×570×1/2= 570m

 

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Question-Answer civil engineering study

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