The British National Grid co ordinate system defines a point as being X
metres East and Y metres North of an origin off the Scilly Isles. The
Scilly Isles is chosen so that all all the values are positive. Since these
measurements are in metres the distance in metres between the points can be
calculated using Pythagoras Theorem.
Theorem, a² + b² = c² where c is the hypotenuse while a and b are the
sides of a right angled triangle.
For calculating the distance d between two co-ordinates (x1, y1) and (x2,
y2) the formula would be:
d² = (x1 - x2)² + (y1 - y2)²
