5.1.1.3 Recommendation.— The wind direction indicator
should be in the form of a truncated cone made of fabric
and should have a length of not less than 3.6 m and a
diameter, at the larger end, of not less than 0.9 m. It should
be constructed so that it gives a clear indication of the
direction of the surface wind and a general indication of the
wind speed. The colour or colours should be so selected as to
make the wind direction indicator clearly visible and
understandable from a height of at least 300 m, having regard
to background. Where practicable, a single colour, preferably
white or orange, should be used. Where a combination of two
colours is required to give adequate conspicuity against
changing backgrounds, they should preferably be orange and
white, red and white, or black and white, and should be
arranged in five alternate bands, the first and last bands being
the darker colour.