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Refer to figure.
What does this symbol indicate on a South African 1 : 1 000 000 aeronautical chart?

  • A

    A meridian of longitude

  • B

    An isogonal

  • C

    An FIR boundary

  • D

    A parallel of latitude

Refer to figure.
According to ICAO Annex 4 - Aeronautical Charts, the symbol indicates an isogonal.

Isogonals are lines on a map or chart joining places of equal magnetic variation. Isogonals are shown as broken lines on the chart, with the value of variation marked alongside. These lines help in understanding how the magnetic variation changes across different regions. The isogonals converge at both the magnetic poles and the true poles.

More specifically, the symbol in the figure indicates an isogonal of 23°W, which joins places where the Magnetic North is located to the west of the geographic (true) north pole by 23°, or the magnetic track is greater than the true track by 23°.

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