Talk:Ordnance Survey National Grid

message: This article should compare (or at least reference) other national and international grid systems.  18.26.0.18 22:14, 19 Feb 2005 (UTC)
thread_title: Untitled 1

message: Does anyone know what significance these letters have? I can guess South, North, and Highlands, but why T (or indeed O)? — Preceding unsigned comment added by PeteVerdon (talk • contribs) 00:18, 18 May 2005‎ (UTC)
:The South and North thing is just a coincidence. The first letters follow the same pattern as the 2nd. Eg look at square NS (west central Scotland). To the east is NT, to the north NN, with NO to the east of that, and NH above NN. It's just alphabetic. Grinner 08:33, May 18, 2005 (UTC)
::There's a map of the top-level grid here . --Heron 18:11, 21 May 2005 (UTC)
replies: text: And, more fully, here . John Wheater 08:49, 22 September 2006 (UTC)
replies: text: Why does it start there then? It's the British National Grid, so surely we should have AA in Britain?  — Preceding unsigned comment added by 77.100.105.162 (talk) 23:03, 28 February 2021 (UTC)
thread_title:  S, T, N, & H 

message: Under the All-numeric grid references  section the article says: " Note that 14 digits may be required for locations in Orkney and futher north".   Square HY is over 1000 km north of the origin, square HU (shetland) is over 1100 km north, which explains why the northing all-numeric reference for Sullom Voe starts with 11.  It's only between  400 and 500km east of the origin so the easting starts with a 4.  That makes 13 digits for the full reference - I can't see why the article quotes 14 for Orkney unless a standardised form requires a "0" to be included.  Then the Sullom Voe reference would be  0439668,1175316 .   Not for me to make the edit though, needs somebody with a better detailed knowledge of OS rules.Mountainwalker (talk) 17:22, 7 March 2020 (UTC)
replies: text: The number of digits for easting and for northing must be the same. This makes it easy to determine where one ends and the other starts. Therefore, the total number of digits must be even. --Redrose64 🌹 (talk) 21:23, 7 March 2020 (UTC)
replies: text: Though the article says 14 figures may be needed, only 13 are displayed, given that (the bulk of) Shetland appears in the 100x100km square 'HU' whose southwestern corner is 400km east of the grid origin and 1100km north of it. That discrepancy between what is stated and what the reader of Wikipedia sees needs further clarification. Similarly in west Cornwall and Scilly, one will sometimes see fewer digits employed because the initial digit may be a zero. The tidal observatory in Newlyn, to choose a suitable example, is at 146762, 28560 (eleven digits) according to some displays, whereas it could also be portrayed as 146762, 028560 (or indeed SW 46762 28560). The former museum in Hugh Town, Scilly is at 90478, 10539 (ten digits)(or 090478, 010539 or indeed SV 90478 10539). Geopersona (talk) 19:32, 23 October 2022 (UTC)
replies: text: OK, but the point is that the input value must have an even number of digits, because it must be split exactly half-way. How it is displayed is not a factor there. --Redrose64 🌹 (talk) 20:40, 23 October 2022 (UTC)
thread_title:  Query about All-numeric grid references