There has long been debate over the exact location of the geographical centre of the United Kingdom, and its constituent countries, due to the complexity and method of the calculation, such as whether to include offshore islands, and the fact that erosion will cause the position to change over time. There are two main methods of calculating this "centre": either as the centroid of the two-dimensional shape made by the country (projected to the Airy ellipsoid then flattened using the Transverse Mercator projection), or as the point farthest from the boundary of the country (either the sea, or, in the case of constituent countries, a land border). These two methods give quite different answers. Traditional locations The town of Haltwhistle in Northumberland has banners stating that it is the "Centre of Britain". By another calculation the centre can also be said to be Dunsop Bridge, Lancashire, 71 miles (114 km) to the south. However, in 2002 the Ordnance Survey conducted studies that pinpointed the respective centres more precisely, and it is their results that are quoted below. Centroid locations Put simply, the centroid is the point at which a cardboard cut-out of the area could be perfectly balanced on the tip of a pencil. Islands are assumed fixed to the mainland in their precise position by invisible rigid weightless wires. A mathematical method is used to do the balancing to a much greater accuracy than the practical method could achieve. Unless stated, positions are the centroids of the two-dimensional shapes made by the countries. Calculations include offshore islands unless stated. United Kingdom A position "in the middle of Morecambe Bay", approximately off the coast at Morecambe (#2), Lancashire, at Ordnance Survey . Great Britain Whitendale Hanging Stones (#1 on the map), near Brennand Farm, outside Dunsop Bridge, Lancashire in the Forest of Bowland.(; ) Great Britain (mainland only) A field south of Calderstones Partnership NHS Foundation Trust (#3), near Whalley, Lancashire () England Lindley Hall Farm (#4), Leicestershire (near Fenny Drayton and Higham on the Hill) (; ) A plaque denoting this point, and disputing the "traditional" centre of England as being at Meriden in the West Midlands, was erected by Ordnance Survey on 14 June 2013 Northern Ireland Annaghone (#5), near Cookstown, County Tyrone ( ) Irish grid ref H 84494 74047. Scotland Between Blair Atholl (#6) and Dalwhinnie, Perthshire (; ) Wales Near Cwmystwyth (#7), Devil's Bridge, Ceredigion