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I'm looking at the definition of a danger area in an AIP section "ENR 5.1 Prohibited, restricted and danger areas", and it's the following.

From 240630N 0543000E counter clockwise along an ARC
of 5.2 NM radius centred on
240400N 0543500E to
240440N 0544040E to
240630N 0543600E to
240630N 0543000E

from this I understand that the distance between the center 240400N, 0543500E and the first point 240630N, 0543000E should be 5.2 NM, but when I calculate the distance between this two points I get 5.685 km or around 3.07 NM.

Why am I getting a different result than what's in the definition incorrectly?

enter image description here

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The coordinates you show are given in the format of degrees, minutes and seconds, not degrees with decimals. If you enter the coordinates in the correct format, you get the desired result:

Great Circle Distance Calculator
(movable-type.co.uk)

The distance of 9.645 km corresponds to 5.208 NM.

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  • $\begingroup$ I completely missed that, thank you. $\endgroup$
    – Bobby Tables
    Aug 26, 2021 at 13:43
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    $\begingroup$ Easily missed when the format doesn't provide any clues. If it was "054.3500 E" you could expect decimal. If it was "054 35 00 E" you could reasonably expect DMS. "0543500E" is... well, you better hope you have the standards document to consult. $\endgroup$
    – hobbs
    Aug 27, 2021 at 4:46
  • $\begingroup$ @hobbs You're right, that is a horrible way of writing the coordinates, especially because the usual format for coordinates in aviation (at least as printed on charts) is degrees, minutes and decimals for minutes (not seconds). I guess it comes from the original definition of a nautical mile (one arc minute of latitude). $\endgroup$
    – Bianfable
    Aug 27, 2021 at 8:30

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