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On a direct Mercator projection, the distance measured between two Meridians spaced 5° apart at latitude 60°N is 8 cm. What is the approximate scale of this chart at latitude 60°N?
  • A
    1: 3 500 000
  • B
    1: 4 750 000
  • C
    1: 6 000 000
  • D
    1: 7 000 000

(1) Determine the Earth distance of Meridians 5° apart at 60ºN, using the departure formula:
Departure (NM) = Longitude Change x 60 x cos (lat)
Departure (NM) = 5º x 60 x cos (60º)
Departure (cm) = 5º x 60 x cos (60º) x 1 852 x 100 cm (as 1 Nm = 1 852 m)

(2) Calculate the Scale at 60ºN
Scale = Chart Distance / Earth Distance
Scale = 8 cm / (5º x 60 x cos 60º x 1 852 x 100 cm)
Scale = 1 / 3 472 500

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