Ghost trigs
Introduction
Early editions of Ordnance Survey maps typically used a triangulation symbol to depict the location of stations in the 19thC Principal Triangulation. Later maps used the same symbol for all OSGB36 stations. Subsequently, the symbol was used only for OSGB36 triangulation pillars. However, a few of the non-pillar symbols were retained (possibly by oversight).
The unwary might therefore find a monument, mast, rivet or suchlike where, from the map, a pillar was expected.
Current maps
'Ghost trig' (or 'Phantom trig') is a term sometimes used to refer to triangulation symbols, on current or recent editions of Ordnance Survey 1:25000 Outdoor Leisure and Explorer maps, which don't correspond to a pillar. Arguably, 'Non-pillar trig symbol' is a more accurate term, albeit unwieldy.
The following table, which is by no means complete, contains some examples [notes 1].
| T:UK | Station name | Grid Reference | Location | Type | Order | map details |
|---|---|---|---|---|---|---|
| TP10666 | Richmond Hill Water Tower | NZ 08066 70637 | Northumberland | Bolt | 3 | Explorer 316 (Newcastle) Edition A (Revised 2000) |
| TP11085 | BP Radar Mast | SM 89492 03699 | Dyfed | Mast | 4 | Outdoor Leisure Map, 1995 |
| TP14052 | Whitechapel | SS 75951 28047 | Devon | Bolt | 3 | Explorer 127 (South Molton) |
| TP17066 | White Moss Farm | SD 35776 13897 | Lancashire | Rivet | 4 | Explorer 285 (Southport & Chorley) Edition A1 (Revised 2007) |
| TP8955 | Dick Hill Monument | SE 01018 05119 | Greater Manchester | Centre | 4 | Outdoor Leisure 1 (The Dark Peak) Edition B (1983) |
| TP18568 | Butt Reservoir | SK 24074 37047 | Derbyshire | Bolt | 3 | Explorer 259 (Derby) Edition A1 (Revised 2005) |
| TP10532 | Swanland Water Tower | SE 98715 27725 | Humberside | Bolt | 3 | Explorer 293 (Hull) Edition A1 (Revised 2006) |
| TP14376 | Victoria Tower Castle Hill | SE 15161 13991 | West Yorkshire | Centre | 3 | Explorer 288 (Bradford & Huddersfield) Edition A (Revised 1999) |
| TP8967 | Cholera Monument | SK 36075 86682 | South Yorkshire | Monument | 3 | Explorer 278 Edition A2 (Revised 2014) |
| TP17491 | Went Hill Resr | SE 47620 18525 | West Yorkshire | Bolt | 4 | Explorer 278 (Sheffield & Barnsley) Edition A2 (Revised 2014) |
| TP10852 | Swingate Water Tower | SK 49983 43849 | Nottinghamshire | Centre | 3 | Explorer 260 (Nottingham) Edition A (Revised 1999) |
| TP18977 | The Wharf | SK 51261 31644 | Nottinghamshire | Bolt | 4 | Explorer 260 (Nottingham) Edition A (Revised 1999) |
| TP7485 | Toton East | SK 49455 34003 | Nottinghamshire | Bolt | 4 | Explorer 260 (Nottingham) Edition A (Revised 1999) |
| TP7411 | Stanedge Pole | SK 24684 84426 | South Yorkshire | Pole | 4 | Explorer OL1 (The Peak District) Edition A2 (Revised 2005) |
| TP9038 | Wainmans Pinnacle | SD 98461 42909 | North Yorkshire | Pinnacle | 3 | Explorer OL21 (South Pennines) Edition A1 (Revised 1996) |
| TP7378 | Stoodley Pike | SD 97304 24206 | West Yorkshire | Monument | 3 | Explorer OL21 (South Pennines) Edition A1 (Revised 1996) |
| TP7408 | Light Hazzles Edge | SD 96278 19358 | Greater Manchester | Bolt | 4 | Explorer OL21 (South Pennines) (Revised 1984) |
| TP17451 | Dialstone Mast | SE 51848 84370 | North Yorkshire | Mast | 4 | Outdoor Leisure 26 (North York Moors - West sheet) (1981) |
| TP17466 | Calver Hill | NZ 01335 00299 | North Yorkshire | Bolt | 3 | Outdoor Leisure 30 (Yorkshire Dales) (1984) |
| TP8048 | Iron Crag | NY 12324 11923 | Cumbria | Bolt | 3 | Outdoor Leisure OL4 (Lake District - North western) (1982) |
| TP15365 | Am Meallan | NG 86667 33984 | Highland Region | Bolt | 4 | Explorer 428 Kyle of Lochalsh, Plockton and Applecross 1:25000 [1] |
| TP15473 | Glenborrowdale | NM 60266 61243 | Highland Region | Bolt | 4 | Landranger 40 Mallaig and Glenfinnan 1:50000 [2] |
| TP15483 | Torr Na Fhaire | NM 67766 44508 | Highland Region | Bolt | 4 | Explorer 383 Morvern and Lochaline 1:25000 [3] |
| TP15291 | Rudh Ard Bhaideanach | NC 41196 55865 | Highland Region | Bolt | 4 | Explorer 446 Durness and Cape Wrath 1:25000 [4] |
| TP13497 | Dunham Massey Crematorium Tower | SJ 73807 89786 | Greater Manchester | Rivet | 4 | Memory-Map 1:25000 England-Wales 2026 [5] |
Earlier map s
OS One-Inch (~1950) [6]. and 1:25000 Pathfinder maps (~1980) often contained non-pillar trig symbols.
Notes
- ↑ More recent editions of these maps have not been checked but some of the trig symbols may have been removed.