D'oh! Just measured the Halton circle on GoogleEarth and it is 82yds in diameter. Also, an article in Flight in January 1919 reporting on the ‘Civil Aerial Transport Committee’ stated:
Marking - It is difficult from the air to distinguish landing grounds from the surrounding country, and they, therefore, require marking in a distinctive manner. A chalk circle 100 ft. in diameter and with a band 3 ft wide, has proved very effective, and can be seen from practically any attainable height on a clear day. It is necessary to keep the sign a good white colour so that it stands out well, and this is done by lime-washing the chalk from time to time. The name of the ground should also be marked in chalk letters 15 ft. long by 3 ft. wide. Emergency grounds should have a distinctive sign to distinguish them from regular landing grounds.
So my info on the circle looks 'duff' unless anyone knows different?
It's still the only RAF airfield left with a chalk circle that I'm aware of though...
LJ
