31-681: Llangynog ( Welsh pronunciation ; grid reference SJ053261 ) is a village and community at the confluence of the Afon Eirth and the Afon Tanat at the foot of the Berwyn range in north Powys (previously Montgomeryshire ), Wales . It lies at the foot of the Milltir Cerrig mountain pass on the B4391 road, which runs between Llan Ffestiniog and Llanfyllin (though
62-529: A 100 m square. For example, the grid reference of the 100 m square containing the summit of Ben Nevis is NN 166 712 . (Grid references may be written with or without spaces; e.g., also NN166712.) NN has an easting of 200 km and northing of 700 km, so the OSGB36 National Grid location for Ben Nevis is at 216600, 771200. Grid references may also be quoted as a pair of numbers: eastings then northings in metres, measured from
93-534: A 5.60% increase since the 321 people noted in 2001 . The 2011 census showed 36.7% of the population could speak Welsh , a fall from 50.6% in 2001, reportedly due to an influx of residents from the West Midlands. 52°49′30″N 3°24′22″W / 52.825°N 3.406°W / 52.825; -3.406 Ordnance Survey National Grid The Ordnance Survey National Grid reference system ( OSGB ), also known as British National Grid ( BNG ),
124-499: A military grid. Four of these largest squares contain significant land area within Great Britain: S, T, N and H. The O square contains a tiny area of North Yorkshire , Beast Cliff at OV 0000 , almost all of which lies below mean high tide. For the second letter, each 500 km square is subdivided into 25 squares of size 100 km by 100 km, each with a letter code from A to Z (again omitting I) starting with A in
155-752: A point in the Atlantic Ocean well to the west of Great Britain. In Cornwall , the WGS 84 longitude lines are about 70 metres east of their OSGB 36 equivalents, this value rising gradually to about 120 m east on the east coast of East Anglia . The WGS 84 latitude lines are about 70 m south of the OSGB 36 lines in South Cornwall , the difference diminishing to zero in the Scottish Borders , and then increasing to about 50 m north on
186-527: Is a system of geographic grid references , distinct from latitude and longitude , whereby any location in Great Britain can be described in terms of its distance from the origin (0, 0), which lies to the west of the Isles of Scilly . The Ordnance Survey (OS) devised the national grid reference system, and it is heavily used in its survey data, and in maps based on those surveys, whether published by
217-461: Is applied. This creates two lines of longitude about 180 km east and west of the central meridian along which the local scale factor equals 1, i.e. map scale is correct. Inside these lines the local scale factor is less than 1, with a minimum of 0.04% too small at the central meridian. Outside these lines the local scale factor is greater than 1, and is about 0.04% too large near the east and west coasts. Grid north and true north are only aligned on
248-470: Is close to the pilgrimage shrine of Saint Melangell at the church of Pennant Melangell ( grid reference SJ024265 ). The community of Pen-y-Bont-Fawr neighbours the community of Llangynog and has a population of 440 as of the 2011 UK Census . It falls under the Llanwddyn electoral ward for elections to Powys County Council . Llangynog's population was 339, according to the 2011 census ;
279-569: Is published by the Ordnance Survey is called the National Grid Transformation OSTN15. This models the detailed distortions in the 1936–1962 retriangulation, and achieves backwards compatibility in grid coordinates to sub-metre accuracy. The difference between the coordinates on different datums varies from place to place. The longitude and latitude positions on OSGB 36 are the same as for WGS 84 at
310-620: Is the system commonly used for the Channel Islands . European-wide agencies also use UTM when mapping locations, or may use the Military Grid Reference System (MGRS), or variants of it. The first letter of the British National Grid is derived from a larger set of 25 squares of size 500 km by 500 km, labelled A to Z, omitting one letter (I) (refer diagram below), previously used as
341-701: The English Channel halfway between Dover and Calais , the ED50 longitude lines are about 20 m east of the OSGB36 equivalents, and the ED50 latitude lines are about 150 m south of the OSGB36 ones. Irish Transverse Mercator Irish Transverse Mercator ( ITM ) is the geographic coordinate system for Ireland. It was implemented jointly by the Ordnance Survey Ireland (OSi) and
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#1732800730064372-628: The English Channel which lies between the island of Jersey and the French port of St. Malo ). Over the Airy ellipsoid a straight line grid, the National Grid, is placed with a new false origin to eliminate negative numbers, creating a 700 km by 1300 km grid. This false origin is located south-west of the Isles of Scilly. In order to minimize the overall scale error, a factor of 2499/2500
403-685: The Isle of Man ). The Irish grid reference system is a similar system created by the Ordnance Survey of Ireland and the Ordnance Survey of Northern Ireland for the island of Ireland. The Irish Transverse Mercator (ITM) coordinate reference system was adopted in 2001 and is now the preferred coordinate reference system across Ireland. ITM is based on the Universal Transverse Mercator coordinate system (UTM), used to provide grid references for worldwide locations, and this
434-543: The Ordnance Survey of Northern Ireland (OSNI) in 2001. The name is derived from the Transverse Mercator projection it uses and the fact that it is optimised for the island of Ireland. The older Irish grid reference system required GPS measurements to be "translated" (using co-ordinate transformations ). The more precise the GPS measurements were, the more the translation process introduced inaccuracies. While
465-495: The Y axis ) The equivalent Irish Grid co-ordinate for the same location is: The Spire of Dublin example provides a fix for a location that is accurate to 1 metre. With ITM it is possible to give a more accurate co-ordinate for a given location by using a decimal point after the initial six figure easting and northing. The ITM co-ordinate for the passive GPS station at the OSi office is: This ITM co-ordinate has three digits behind
496-616: The B4391 road number 'disappears' between the western end of Llyn Celyn and Bala ). It is surrounded by mountains including Craig Rhiwarth and is a popular base for walkers . Llangynog has a down-hill mountain bike course, and a crown green bowling club, who play in the Oswestry League. It was the western terminus of the Tanat Valley Light Railway (Llynclys - Llangynog) (15 miles); it opened on 5 January 1904 and closed (passenger traffic) in 1951. It
527-465: The Ordnance Survey or by commercial map producers. Grid references are also commonly quoted in other publications and data sources, such as guide books and government planning documents. A number of different systems exist that can provide grid references for locations within the British Isles : this article describes the system created solely for Great Britain and its outlying islands (including
558-525: The central meridian (400 km easting) of the grid which is 2° W (OSGB36) and approx. 2° 0′ 5″ W ( WGS 84 ). A geodetic transformation between OSGB 36 and other terrestrial reference systems (like ITRF2000 , ETRS89 , or WGS 84 ) can become quite tedious if attempted manually. The most common transformation is called the Helmert datum transformation , which results in a typical 7 m error from true. The definitive transformation from ETRS89 that
589-484: The decimal point which gives a fix for a location with millimetre accuracy. Also notice how the easting in this example is indicated with an “E” and likewise an “N” for the northing. The fact that the co-ordinate is in metres is indicated by the lowercase m. With ITM there is no provision for using myriad letters and truncated coordinates as there is with the Irish Grid . Every co-ordinate must be given with at least
620-497: The existing UTM co-ordinate system partly fulfilled the requirement for direct GPS compatibility it had some drawbacks, including varying levels of distortion across the island due to the central meridian being at the west coast of Ireland. The new system needed to satisfy various criteria: GPS compatibility, map distortion for the whole island of Ireland had to be minimal, it was to be conformal and backward compatible with existing mapping. A customised Transverse Mercator projection
651-453: The north coast of Scotland . (If the lines are further east , then the longitude value of any given point is further west . Similarly, if the lines are further south, the values will give the point a more northerly latitude.) The smallest datum shift is on the west coast of Scotland and the greatest in Kent . These two datums are not both in general use in any one place, but for a point in
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#1732800730064682-429: The north-west corner to Z in the south-east corner. These squares are outlined in light grey on the "100km squares" map, with those containing land lettered. The central (2° W) meridian is shown in red. Within each square, eastings and northings from the south west corner of the square are given numerically. For example, NH0325 means a 1 km square whose south-west corner is 3 km east and 25 km north from
713-474: The older Irish Grid format into the future, the Irish Institution of Surveyors has recommended that ITM be adopted as soon as possible as the preferred official co-ordinate system for Ireland. An ITM co-ordinate is generally given as a pair of two six-digit numbers (excluding any digits behind a decimal point which may be used in very precise surveying). The first number is always the easting and
744-451: The second is the northing . The easting and northing are in metres from the false origin . The ITM co-ordinate for the Spire of Dublin on O'Connell Street is: The first figure is the easting and means that the location is 715,830 metres east from the false origin (along the X axis ). The second figure is the northing and puts the location 734,697 metres north of the false origin (along
775-427: The south-west corner of square NH. A location can be indicated to varying resolutions numerically, usually from two digits in each coordinate (for a 1 km square) through to five (for a 1 m square); in each case the first half of the digits is for the first coordinate and the second half for the other. The most common usage is the six figure grid reference , employing three digits in each coordinate to determine
806-405: The south-west to NN400900 in the north-east) the abbreviated grid reference 166712 is equivalent to NN166712. If working with more than one Landranger sheet, this may also be given as 41/166712. Alternatively, sometimes numbers instead of the two-letter combinations are used for the 100×100 km squares. The numbering follows a grid index where the tens denote the progress from West to East and
837-554: The southwest corner of the SV square. 13 digits may be required for locations in Orkney and further north. For example, the grid reference for Sullom Voe Oil Terminal in the Shetland islands may be given as HU396753 or 439668,1175316 . Another, distinct, form of all-numeric grid reference is an abbreviated alphanumeric reference where the letters are simply omitted, e.g. 166712 for
868-722: The standard projection for Ordnance Survey maps. The Airy ellipsoid is a regional best fit for Britain; more modern mapping tends to use the GRS80 ellipsoid used by the Global Positioning System (the Airy ellipsoid assumes the Earth to be about 1 km smaller in diameter than the GRS80 ellipsoid, and to be slightly less flattened). The British maps adopt a transverse Mercator projection with an origin (the "true" origin) at 49° N , 2° W (an offshore point in
899-470: The summit of Ben Nevis. Unlike the numeric references described above, this abbreviated grid reference is incomplete; it gives the location relative to an OS 100×100 km square, but does not specify which square. It is often used informally when the context identifies the OS 2-letter square. For example, within the context of a location known to be on OS Landranger sheet 41 (which extends from NN000500 in
930-588: The units from South to North. In the north of Scotland, the numbering is modified: the 100 km square to the north of 39 is numbered N30; the square to the north of 49 is N40, etc. The grid is based on the OSGB36 datum (Ordnance Survey Great Britain 1936, based on the Airy 1830 ellipsoid ), and was introduced after the retriangulation of 1936–1962 . It replaced the Cassini Grid which had previously been
961-524: Was chosen. ITM and the older more established Irish Grid will (initially at least) be used in parallel. As a result ITM coordinates had to be obviously different so users would not confuse the two. This was done by shifting the ITM false origin further into the Atlantic and thereby creating substantially different co-ordinate numbers for any given location. While OSi and OSNI intend to supply map information in