What is Ordnance Survey National Grid?
The '''Ordnance Survey National Grid''' is a system used to map [[Great Britain]]. It is different from using [[latitude]] and [[longitude]]. The [[Ordnance Survey]] (OS) created the system. It is used a lot in their survey data. It is also used in maps based on those surveys. [[File:British National Grid.svg|thumb|right|Squares of the grid system. The red line is the central (2° W) meridian.]] The system divides the map into squares. Each square is labelled with two letters. The first letter refers to squares that are 500&nbsp;km by 500&nbsp;km. Those squares are outlined in dark grey on the map to the right. Only four of these have a lot of land area in Great Britain: S, T, N and H. The O square contains a tiny area of [[North Yorkshire]]. Normally most of this area is submerged at high tide.<ref>Standing, 2006</ref> For the second letter, each 500&nbsp;km square is divided into 25 squares that are 100&nbsp;km by 100&nbsp;km. Each of those has a letter code from A to Z. (The letter ''I'' is not used.) The letters start with A in the northwest corner and go to Z in the southeast corner. These squares are outlined in light grey on the map. The ones that have land have letters shown. The system can also be used to give the location of a smaller area inside a lettered square. This is done by giving the distance east and north from the southwest corner of the square. For example, NH0325 (or NH 03 25) means a one-kilometre square whose southwest corner is 3&nbsp;km east and 25&nbsp;km north from the southwest corner of square NH. The system can also specify areas smaller than one kilometre. For example, the grid reference of the 100-metre square containing the summit of [[Ben Nevis]] is '''{{gbmaprim|NN166712|NN 166 712}}'''. == Notes == {{reflist}} == References == * Standing, Peter (2006) [https://www.geograph.org.uk/article/In-Search-of-OV0000 ''OV0000 a unique grid square at Beast Cliff''], Geograph Project, UK, web article [accessed 11 June 2007] * {{cite web |title=The true origin |url=http://www.ordnances