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The Irish grid reference system is a system of geographic grid references used for paper mapping in Ireland (both Northern Ireland and the Republic of Ireland). [1] The Irish grid partially overlaps the British grid, and uses a similar co-ordinate system but with a meridian more suited to its westerly location.
In general, neither Ireland nor Great Britain uses latitude or longitude in describing internal geographic locations. Instead grid reference systems are used for mapping.
The national grid referencing system was devised by the Ordnance Survey, and is heavily used in their survey data, and in maps (whether published by the Ordnance Survey of Ireland, the Ordnance Survey of Northern Ireland or commercial map producers) based on those surveys. Additionally grid references are commonly quoted in other publications and data sources, such as guide books or government planning documents.
In 2001, the Ordnance Survey of Ireland and the Ordnance Survey of Northern Ireland jointly implemented a new coordinate system for Ireland called Irish Transverse Mercator, or ITM, a location-specific optimisation of UTM, which runs in parallel with the existing Irish grid system. In both systems, the true origin is at 53° 30' N, 8° W [2] — a point in Lough Ree, close to the western (Co. Roscommon) shore, whose grid reference is N000500 . The ITM system was specified so as to provide precise alignment with modern high-precision global positioning receivers.
The area of Ireland is divided into 25 squares, measuring 100 by 100 km (62 by 62 mi), each identified by a single letter. The squares are numbered A to Z with I being omitted. Seven of the squares do not actually cover any land in Ireland: A, E, K, P, U, Y and Z.
Within each square, eastings and northings from the origin (south west corner) of the square are given numerically. For example, G0305 means 'square G, 3 km (1.9 mi) east, 5 km (3.1 mi) north'. A location can be indicated to varying resolutions numerically, usually from two digits in each coordinate (for a 1 km (0.62 mi) square) through to five (for a 1 m (3 ft 3 in)) square; the most common usage is the six figure grid reference, employing three digits in each coordinate to determine a 100 m (330 ft) square.
Coordinates may also be given relative to the origin of the entire 500 by 500 km (310 by 310 mi) grid (in the format easting, northing). For example, the location of the Spire of Dublin on O'Connell Street may be given as 315904, 234671 as well as O1590434671. Coordinates in this format must never be truncated, because, for example, 31590, 23467 is also a valid location.
A projected coordinate system, also known as a projected coordinate reference system, a planar coordinate system, or grid reference system, is a type of spatial reference system that represents locations on the Earth using cartesian coordinates (x,y) on a planar surface created by a particular map projection. Each projected coordinate system, such as "Universal Transverse Mercator WGS 84 Zone 26N," is defined by a choice of map projection, a choice of geodetic datum to bind the coordinate system to real locations on the earth, an origin point, and a choice of unit of measure. Hundreds of projected coordinate systems have been specified for various purposes in various regions.
The Ordnance Survey National Grid reference system is a system of geographic grid references used in Great Britain, distinct from latitude and longitude.
The transverse Mercator map projection is an adaptation of the standard Mercator projection. The transverse version is widely used in national and international mapping systems around the world, including the Universal Transverse Mercator. When paired with a suitable geodetic datum, the transverse Mercator delivers high accuracy in zones less than a few degrees in east-west extent.
The Military Grid Reference System (MGRS) is the geocoordinate standard used by NATO militaries for locating points on Earth. The MGRS is derived from the Universal Transverse Mercator (UTM) grid system and the Universal Polar Stereographic (UPS) grid system, but uses a different labeling convention. The MGRS is used as geocode for the entire Earth.
The Swiss coordinate system is a geographic coordinate system used in Switzerland and Liechtenstein for maps and surveying by the Swiss Federal Office of Topography (Swisstopo).
The equirectangular projection, and which includes the special case of the plate carrée projection, is a simple map projection attributed to Marinus of Tyre, who Ptolemy claims invented the projection about AD 100. The projection maps meridians to vertical straight lines of constant spacing, and circles of latitude to horizontal straight lines of constant spacing. The projection is neither equal area nor conformal. Because of the distortions introduced by this projection, it has little use in navigation or cadastral mapping and finds its main use in thematic mapping. In particular, the plate carrée has become a standard for global raster datasets, such as Celestia, NASA World Wind, and Natural Earth, because of the particularly simple relationship between the position of an image pixel on the map and its corresponding geographic location on Earth. In addition it is frequently used in panoramic photography to represent a spherical panoramic image.
Ordnance Survey Ireland is the national mapping agency of Ireland. It was established on 4 March 2002 as a body corporate. It is the successor to the former Ordnance Survey of Ireland. It and the Ordnance Survey of Northern Ireland (OSNI) are the ultimate successors to the Irish operations of the British Ordnance Survey. OSI is part of the Irish public service. OSI has made modern and historic maps of the state free to view on its website. OSI is headquartered at Mountjoy House in the Phoenix Park in Dublin. Mountjoy House was also the headquarters, until 1922, of the Irish section of the British Ordnance Survey.
Ordnance Survey of Northern Ireland (OSNI) was the official mapping agency of Northern Ireland. The agency ceased to exist separately on 1 April 2008 when it became part of Land and Property Services, an executive agency of the Northern Ireland Department of Finance and Personnel, along with the Rate Collection Agency, the Valuation and Lands Agency, and the Land Registry.
ED50 is a geodetic datum which was defined after World War II for the international connection of geodetic networks.
The Universal Transverse Mercator (UTM) is a map projection system for assigning coordinates to locations on the surface of the Earth. Like the traditional method of latitude and longitude, it is a horizontal position representation, which means it ignores altitude and treats the earth as a perfect ellipsoid. However, it differs from global latitude/longitude in that it divides earth into 60 zones and projects each to the plane as a basis for its coordinates. Specifying a location means specifying the zone and the x, y coordinate in that plane. The projection from spheroid to a UTM zone is some parameterization of the transverse Mercator projection. The parameters vary by nation or region or mapping system.
A spatial reference system (SRS) or coordinate reference system (CRS) is a framework used to precisely measure locations on the surface of the Earth as coordinates. It is thus the application of the abstract mathematics of coordinate systems and analytic geometry to geographic space. A particular SRS specification comprises a choice of Earth ellipsoid, horizontal datum, map projection, origin point, and unit of measure. Thousands of coordinate systems have been specified for use around the world or in specific regions and for various purposes, necessitating transformations between different SRS.
The World Geographic Reference System (GEOREF) is a geocode, a grid-based method of specifying locations on the surface of the Earth. GEOREF is essentially based on the geographic system of latitude and longitude, but using a simpler and more flexible notation. GEOREF was used primarily in aeronautical charts for air navigation, particularly in military or inter-service applications, but it is rarely seen today. However, GEOREF can be used with any map or chart that has latitude and longitude printed on it.
The United States National Grid (USNG) is a multi-purpose location system of grid references used in the United States. It provides a nationally consistent "language of location", optimized for local applications, in a compact, user friendly format. It is similar in design to the national grid reference systems used in other countries. The USNG was adopted as a national standard by the Federal Geographic Data Committee (FGDC) of the US Government in 2001.
The State Plane Coordinate System (SPCS) is a set of 124 geographic zones or coordinate systems designed for specific regions of the United States. Each state contains one or more state plane zones, the boundaries of which usually follow county lines. There are 110 zones in the contiguous US, with 10 more in Alaska, 5 in Hawaii, and one for Puerto Rico and US Virgin Islands. The system is widely used for geographic data by state and local governments. Its popularity is due to at least two factors. First, it uses a simple Cartesian coordinate system to specify locations rather than a more complex spherical coordinate system. By using the Cartesian coordinate system's simple XY coordinates, "plane surveying" methods can be used, speeding up and simplifying calculations. Second, the system is highly accurate within each zone. Outside a specific state plane zone accuracy rapidly declines, thus the system is not useful for regional or national mapping.
Irish Transverse Mercator (ITM) is the geographic coordinate system for Ireland. It was implemented jointly by the Ordnance Survey Ireland (OSi) and 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.
Israeli Transverse Mercator (ITM), also known as the New Israel Grid is the new geographic coordinate system for Israel. The name is derived from the transverse Mercator projection it uses and the fact that it is optimized for Israel. ITM has replaced the old coordinate system Israeli Cassini Soldner (ICS), also known as the Old Israel Grid (OIG). It became the official grid for Israel in 1998.
Israeli Cassini Soldner (ICS), commonly known as the Old Israeli Grid is the old geographic coordinate system for Israel. The name is derived from the Cassini Soldner projection it uses and the fact that it is optimized for Israel. ICS has been mostly replaced by the new coordinate system Israeli Transverse Mercator (ITM), also known as the New Israeli Grid (NIG), but still referenced by older books and navigation software.
The article Transverse Mercator projection restricts itself to general features of the projection. This article describes in detail one of the (two) implementations developed by Louis Krüger in 1912; that expressed as a power series in the longitude difference from the central meridian. These series were recalculated by Lee in 1946, by Redfearn in 1948, and by Thomas in 1952. They are often referred to as the Redfearn series, or the Thomas series. This implementation is of great importance since it is widely used in the U.S. State Plane Coordinate System, in national and also international mapping systems, including the Universal Transverse Mercator coordinate system (UTM). They are also incorporated into the Geotrans coordinate converter made available by the United States National Geospatial-Intelligence Agency. When paired with a suitable geodetic datum, the series deliver high accuracy in zones less than a few degrees in east-west extent.
The geographical centre of Ireland, according to an investigation and calculation carried out by the Official Irish Government Mapping Agency, Ordnance Survey Ireland (OSi)(as published on the official OSi website on 24th February 2022) is near the community of Castletown Geoghegan, about 14kms from Mullingar in County Westmeath and lies at the Irish Transverse Mercator (ITM) coordinates 633015.166477, 744493.046768, [Reference : Ordinance Survey Ireland website Blog : https://osi.ie/blog/].
The Palestine grid was the geographic coordinate system used by the Survey Department of Palestine.