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Using the following data, estimate the approximate distance between points "A" and "B" based on the following information:

Scale of a Direct Mercator chart at the equator: 1:200 000
Chart length between 'A' and 'B' near the equator: 11 cm.

  • A
    12 NM
  • B
    14 NM
  • C
    21 NM
  • D
    22 NM

The chart's scale illustrates the relationship between the depicted length on the chart and the actual distance on Earth's surface.

Chart Scale = Chart length / Earth distance

So, with the given information:

1/200 000 = 11 cm / Earth Distance

To find Earth's distance:

Earth Distance = 200 000 x 11 cm
Earth Distance = 2 200 000 cm = 22 km

In this scenario, as the units of length in the options are in different formats, we need to convert them to a common unit:

1.852 km = 1 NM
22 km = 11.88 NM (approx. 12 NM)


Alternatively, you can use the Flight computer (CRP5):

  1. Align 22 km on the inner scale with the "km" index on the Outer Scale.
  2. Read 12 NM on the inner scale against the "Naut M" index on the Outer scale.

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