The Great Millennium
Circle - coordinates
by Robert McCaffrey
These pages give you the coordinates for the Great Millennium Circle. The were calculated by defining three 'constraining' points on the circle (The centre of the Severn Bridge, Fosdyke Bridge over the River Witham close to the Wash, and a point on the northern bank of the Manchester Ship Canal, next to the Mersey Estuary). The centre of the circle was then iteratively calcualted (does anyone know a better way?), to define the centre of the circle, with the three points on the edge of the circle then, by definition, all being at the same distance away and giving you the radius of the circle.
With the map coordinates of the centre and the radius of the circle now known, I used a spreadsheet and a bit of elementary geometry to calculate a map coordinate for each degree of the circle.
The coordinates are given as ten-figures references (to the nearest 10m), but you could define the perfect circle down to the nearest millimetre if you wanted to (it would be rather pointless though). You will also find a description of a geographical feature close to that point on the circle, and the identity of the Landranger Ordinance Survey map you would be using for that section of the circle.
Happy walking (or cycling!).
Coordinates