To FootSee "About This JavaScript Site" in JavaScript Index and Introduction.
SEE Vincenty formula for distance between two Latitude/Longitude points.
For a more authoritative source of information, look around at the Ordnance Survey site. This page is provided only as a JavaScript and geometry demonstration, not as a precision tool.
Do not use this page repeatedly. If needed, you can copy it to your own computer and use it there; or you can write your own version. But do not re-publish this page itself in any manner.
CAVEAT : approximates as a Pythagorean surface; UNDERTESTED.
A reference is any even number of digits, the first of each half representing 10 km. The Bearing is clockwise from Grid North.
CAVEATS : Geometry is approximate; being changed; UNDERTESTED.
Errors in Scotland may reach ~0.010°.
Known :-
2 degrees West is the Grid line 400 km Eastings, throughout -
Poole to Fraserburgh.
Earth diameter is nominally 40,000 km (origin of SI), so
1 m = 9 µ° in a Great Circle - but the geoid is not a sphere.
50°N 2°W is about 11.5 km Northings - used in (a) here.
49°N 2°W is by definition 400 km Eastings,
100 km Southings - used in (b) here.