Examples
1) The scale of an aerial photograph is 1 cm = 100 m. The photograph size is 20cm x 20cm. Determine the number of photographs required to cover an area of 100 sq. km if the longitudinal lap is 60% and the side lap is 30%.
Solution.
Here l = 20 cm ; w = 20 cm ; P1 = 0.60 ; Pw = 0.30
L = (1 – Pl) sl = (1- 0.6) 100 x 20 = 800 m = 0.8 km
Actual ground width covered by each photograph is
W = (1 – Pw) sw = (1 – 0.3) 100 x 20 = 1400 m = 1.4 km
a = Lx W = 0.8 x 1.4 = 1.12 sq. km
hence number of photographs required is
2) The scale of an aerial photograph is 1cm = 100 m. The photograph size is 20cm x 20xm. Determine the number of photograph required to cover an area 10 km x 10km, if the longitudinal lap is 60% and the side lap is 30%.
Solution
Here L1= 10 km ; L2 = 10 km
Number of flight lines required is given by
Hence number of photographs required will be
The spacing of the flight lines would be 10/9 = 1.11 km and not 1.4 as calculated theoretically in the previous example.
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