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Co-ordinate Systems

GS 84 (GPS Co-ordinates)

We use the World Geodetic System standard co-ordinate system. Co-ordinates are expressed as signed decimal latitude and longitude values. This reference system is also use by the Global Positioning System (GPS).

OSGB36

The Ordnance Survey grid system projects Great Britain onto a 2D system comprising X and Y co-ordinates, in metres. The origin is at a point to the south west of Land's End. The X and Y co-ordinates are referred to as eastings (or east) and northings (or north) respectively.

Note that the OSGB36 grid system applies only to Great Britain and offshore islands - Northern Ireland and the Channel Islands are not included.

Irish Grid Reference System

The island of Ireland uses a similar system to OSGB36; co-ordinates are projected onto a 2D system which covers the island. This is independent from the GB system.

Examples

Great Britain

Here are the approximate positions of some GB places, in WGS 84 and OSGB36.

Name Latitude Longitude X (Eastings) Y (Northings)
London 51.5 -0.126236 530157 179576
Penzance 50.118558 -5.540874 30281 146977
Edinburgh 55.944555 -3.206062 324771 673047
Cardiff 51.491848 -3.194584 317161 177666
Leeds 53.809035 -1.546004 429993 424844
Aberdeen 57.148134 -2.121849 392726 806367
Norwich 52.636641 1.288493 622611 309398

Northern Ireland

Here are the approximate positions of some places in Northern Ireland, in WGS 84 and the Irish Grid Reference System.

Name Latitude Longitude X (Eastings) Y (Northings)
Belfast 54.5757 -5.98257 142717 530157
Coleraine 55.131994 -6.668451 102550 591914
Ballymena 54.863117 -6.278343 125565 560426

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