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96-543: The Ordnance Survey National Grid reference system ( OSGB ), also known as British National Grid ( BNG ), 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

192-599: A government-owned company , 100% in public ownership. The Ordnance Survey Board remains accountable to the Secretary of State for Science, Innovation and Technology . It was also a member of the Public Data Group . Paper maps represent only 5% of the company's annual revenue. It produces digital map data, online route planning and sharing services and mobile apps, plus many other location-based products for business, government and consumers. Ordnance Survey mapping

288-459: A truncated grid reference may be used where the general location is already known to participants and may be assumed. Because the (leading) most significant digits specify the part of the world and the (trailing) least significant digits provide a precision that is not needed in most circumstances, they may be unnecessary for some uses. This permits users to shorten the example coordinates to 949-361 by concealing 05nnn34 56nnn74 , assuming

384-529: 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

480-422: A 6-figure grid reference identifies a square of 100-metre sides, an 8-figure reference would identify a 10-metre square, and a 10-digit reference a 1-metre square. In order to give a standard 6-figure grid reference from a 10-figure GPS readout, the 4th, 5th, 9th and 10th digits must be omitted, so it is important not to read just the first 6 digits. Ordnance Survey#Map range The Ordnance Survey ( OS )

576-656: A close, arranging mountain-top parties with enormous plum puddings . The British Geological Survey was founded in 1835 as the Ordnance Geological Survey under Henry De la Beche , and remained a branch of the Ordnance Survey until 1965. At the same time, the uneven quality of the English and Scottish maps was being improved by engravers under Benjamin Baker . By the time Colby retired in 1846,

672-465: A digit from 0 to 9 (with 0 0 being the bottom left square and 9 9 being the top right square). For the church in Little Plumpton, this gives the digits 6 and 7 (6 on the left to right axis (Eastings) and 7 on the bottom to top axis (Northings). These are added to the four-figure grid reference after the two digits describing the same coordinate axis , and thus our six-figure grid reference for

768-531: A fire in the Tower of London , the headquarters of the survey was moved to Southampton taking over buildings previously occupied by a military orphanage (the Royal Military Asylum ) in 1841, and Yolland was put in charge, but Hall sent him off to Ireland so that when Hall left in 1854 Yolland was again passed over in favour of Major Henry James . Hall was enthusiastic about extending the survey of

864-669: A flat surface of a map. The datum, along with a map projection applied to a grid of reference locations, establishes a grid system for plotting locations. Conformal projections are generally preferred. Common map projections include the transverse mercator (used in Universal Transverse Mercator , the British National Grid , the State Plane Coordinate System for some states), Lambert Conformal Conic (some states in

960-415: A four-digit grid reference describing a one-kilometre square on the ground. The convention is the grid reference numbers call out the lower-left corner of the desired square. In the example map above, the town Little Plumpton lies in the square 6901, even though the writing which labels the town is in 6802 and 6902, most of the buildings (the orange boxed symbols) are in square 6901. The more digits added to

1056-455: A grid reference, the more precise the reference becomes. To locate a specific building in Little Plumpton, a further two digits are added to the four-digit reference to create a six-digit reference. The extra two digits describe a position within the 1-kilometre square. Imagine (or draw or superimpose a Romer ) a further 10x10 grid within the current grid square. Any of the 100 squares in the superimposed 10×10 grid can be accurately described using

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1152-479: A large range of paper maps and digital mapping products. The Ordnance Survey's flagship digital product, launched in November 2001, is OS MasterMap , a database that records, in one continuous digital map, every fixed feature of Great Britain larger than a few metres. Every feature is given a unique TOID (TOpographical IDentifier), a simple identifier that includes no semantic information. Typically, each TOID

1248-554: A map, but it is important to know how many digits the GPS displays to avoid reading off just the first six digits. A GPS unit commonly gives a ten-digit grid reference, based on two groups of five numbers for the Easting and Northing values. Each successive increase in precision (from 6 digit to 8 digit to 10 digit) pinpoints the location more precisely by a factor of 10. Since, in the UK at least,

1344-497: 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

1440-585: A new survey based on Airy 's spheroid in 1858, completing the Principal Triangulation . The following year, he completed an initial levelling of the country. After the Ordnance Survey published its first large-scale maps of Ireland in the mid-1830s, the Tithe Act 1836 led to calls for a similar six-inch to the mile survey in England and Wales . Official procrastination followed, but

1536-752: 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

1632-501: A proportion of its profits to the Treasury. In 2010, OS announced that printing and warehouse operations were to be outsourced, ending over 200 years of in-house printing. The Frome-based firm Butler, Tanner and Dennis (BT&D) secured its printing contract. As already stated, large-scale maps had not been printed at the Ordnance Survey since the common availability of geographical information systems (GISs), but, until late 2010,

1728-587: A resurgence in the use of GCS. That said, projected coordinate systems are still very common in the GIS data stored in the Spatial Data Infrastructures (SDI) of local areas, such as cities, counties, states and provinces, and small countries. Because the purpose of any coordinate system is to accurately and unambiguously measure, communicate, and perform calculations on locations, it must be defined precisely. The EPSG Geodetic Parameter Dataset

1824-477: A second edition of the town plans: by 1909 only fourteen places had paid for updates. The review determined that revision of 1:2500 mapping should proceed apace. The most detailed mapping of London was the OS's 1:1056 survey between 1862 and 1872, which took 326 sheets to cover the capital; a second edition (which needed 759 sheets because of urban expansion) was completed and brought out between 1891 and 1895. London

1920-583: Is associated with a polygon that represents the area on the ground that the feature covers, in National Grid coordinates. OS MasterMap is offered in themed layers, each linked to a number of TOIDs. In September 2010, the layers were: Topography: Integrated transport network: Imagery Address: Address 2: ITN was withdrawn in April 2019 and replaced by OS MasterMap Highways Network The Address layers were withdrawn in about 2016 with

2016-460: 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

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2112-759: Is based on the Universal Transverse Mercator coordinate system (UTM), used to provide grid references for worldwide locations, and this 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

2208-600: Is given a two-digit code, based on the British national grid reference system with an origin point just off the southwest coast of the United Kingdom . The area is divided into 100 km squares, each of which is denoted by a two-letter code. Within each 100 km square, a numerical grid reference is used. Since the Eastings and Northings are one kilometre apart, a combination of a Northing and an Easting will give

2304-478: Is heavily used in its survey data, and in maps based on those surveys, whether published by 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

2400-502: 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

2496-537: Is the national mapping agency for Great Britain. The agency's name indicates its original military purpose (see ordnance and surveying ), which was to map Scotland in the wake of the Jacobite rising of 1745 . There was also a more general and nationwide need in light of the potential threat of invasion during the Napoleonic Wars . Since 1 April 2015, the Ordnance Survey has operated as Ordnance Survey Ltd,

2592-436: Is the most common mechanism for publishing such definitions in a machine-readable form, and forms the basis for many GIS and other location-aware software programs. A projected SRS specification consists of three parts: To establish the position of a geographic location on a map , a map projection is used to convert geodetic coordinates to plane coordinates on a map; it projects the datum ellipsoidal coordinates and height onto

2688-481: Is usually classified as either " large-scale " (in other words, more detailed) or "small-scale". The Survey's large-scale mapping comprises 1:2,500 maps for urban areas and 1:10,000 more generally. (The latter superseded the 1:10,560 "six inches to the mile " scale in the 1950s.) These large scale maps are typically used in professional land-use contexts and were available as sheets until the 1980s, when they were digitised . Small-scale mapping for leisure use includes

2784-597: Is usually represented conventionally with easting first, northing second. For example, the peak of Mount Assiniboine (at 50°52′10″N 115°39′03″W  /  50.86944°N 115.65083°W  / 50.86944; -115.65083 on the British Columbia / Alberta border in Canada ) in UTM Zone 11 is at (0594934mE, 5636174mN) , meaning that is almost 600km east of the false origin for Zone 11 (95km east of

2880-629: The Department for Business, Energy and Industrial Strategy (BEIS) appointed Steve Blair as the Chief Executive of the Ordnance Survey. The Ordnance Survey supported the launch of the Slow Ways initiative, which encourages users to walk on lesser used paths between UK towns. On 7 February 2023, ownership of Ordnance Survey Ltd passed to the newly formed Department for Science, Innovation and Technology . The Ordnance Survey produces

2976-692: 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. Grid reference When the first standardized coordinate systems were created during the 20th century, such as the Universal Transverse Mercator , State Plane Coordinate System , and British National Grid , they were commonly called grid systems ;

Ordnance Survey National Grid - Misplaced Pages Continue

3072-627: 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

3168-660: The Geographic coordinate system (GCS, latitude and longitude) date to the Hellenistic period , proliferating during the Enlightenment Era of the 18th century. However, their use as the basis for specifying precise locations, rather than latitude and longitude, is a 20th century innovation. Among the earliest was the State Plane Coordinate System (SPCS), which was developed in the United States during

3264-619: The OS Explorer and OS Landranger series were printed in Maybush. In April 2009 building began of a new head office in Adanac Park on the outskirts of Southampton. By 10 February 2011 virtually all staff had relocated to the new "Explorer House" building and the old site had been sold off and redeveloped. Prince Philip officially opened the new headquarters building on 4 October 2011. On 22 January 2015 plans were announced for

3360-553: The Ordnance Survey National Grid 1:1250s, 1:2500s and 1:10,560s after the Second World War. During World War I, the Ordnance Survey was involved in preparing maps of France and Belgium . During World War II, many more maps were created, including: After the war, Colonel Charles Close , then Director General, developed a strategy using covers designed by Ellis Martin to increase sales in

3456-644: The Pilgrims' Way in the North Downs labelled the wrong route, but the name stuck. Similarly, the spelling of Scafell and Scafell Pike copied an error on an earlier map, and was retained as this was the name of a corner of one of the Principal Triangles , despite "Scawfell" being the almost universal form at the time. Colby believed in leading from the front, travelling with his men, helping to build camps and, as each survey session drew to

3552-504: The SPCS ), and Mercator ( Swiss coordinate system ). Map projection formulas depend on the geometry of the projection as well as parameters dependent on the particular location at which the map is projected. The set of parameters can vary based on the type of project and the conventions chosen for the projection. For the transverse Mercator projection used in UTM, the parameters associated are

3648-692: The 1930s for surveying and engineering, because calculations such as distance are much simpler in a Cartesian coordinate system than the three-dimensional trigonometry of GCS. In the United Kingdom , the first version of the British National Grid was released in 1938, based on earlier experiments during World War I by the Army and the Ordnance Survey . During World War II , modern warfare practices required soldiers to quickly and accurately measure and report their location, leading to

3744-434: The 1980s with the emergence of geographic information systems . GIS requires locations to be specified as precise coordinates and performs numerous calculations on them, making cartesian geometry preferable to spherical trigonometry when computing horsepower was at a premium. In recent years, the rise of global GIS datasets and satellite navigation , along with an abundance of processing speed in personal computers, have led to

3840-547: The 1:25,000 "Explorer" series, the 1:50,000 "Landranger" series and the 1:250,000 road maps. These are still available in traditional sheet form. Ordnance Survey maps remain in copyright for 50 years after their publication. Some of the Copyright Libraries hold complete or near-complete collections of pre-digital OS mapping. The origins of the Ordnance Survey lie in the aftermath of the Jacobite rising of 1745 . Prince William, Duke of Cumberland realised that

3936-589: The British Army did not have a good map of the Scottish Highlands to locate Jacobite dissenters such as Simon Fraser, 11th Lord Lovat so that they could be put on trial. In 1747, Lieutenant-Colonel David Watson proposed the compilation of a map of the Highlands to help in pacifying the region. In response, King George II charged Watson with making a military survey of the Highlands under

Ordnance Survey National Grid - Misplaced Pages Continue

4032-547: The UK into one-kilometre squares, east of an imaginary zero point in the Atlantic Ocean, west of Cornwall. The grid lines point to a Grid North, varying slightly from True North. This variation is zero on the central meridian (north-south line) of the map, which is at two degrees West of the Prime Meridian , and greatest at the map edges. The difference between grid north and true north is very small and can be ignored for most navigation purposes. The difference exists because

4128-608: The alphanumeric Military Grid Reference System (MGRS) was then created as an encoding scheme for UTM coordinates to make them easier to communicate. After the War, UTM gradually gained users, especially in the scientific community. Because UTM zones do not align with political boundaries, several countries followed the United Kingdom in creating their own national or regional grid systems based on custom projections. The use and invention of such systems especially proliferated during

4224-525: 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

4320-522: The centre of Southampton (made worse by the bomb damage of the Second World War). The bombing during the Blitz devastated Southampton in November 1940 and destroyed most of the Ordnance Survey's city centre offices . Staff were dispersed to other buildings and to temporary accommodation at Chessington and Esher, Surrey, where they produced 1:25000 scale maps of France, Italy, Germany and most of

4416-410: The church becomes 696017. This reference describes a 100-metre by 100-metre square, and not a single point, but this precision is usually sufficient for navigation purposes. The symbols on the map are not precise in any case, for example the church in the example above would be approximately 100x200 metres if the symbol was to scale, so in fact, the middle of the black square represents the map position of

4512-481: The city's court complex. The new head office building was designed by the Ministry of Public Building and Works for 4000 staff, including many new recruits who were taken on in the late 1960s and early 1970s as draughtsmen and surveyors. The buildings originally contained factory-floor space for photographic processes such as heliozincography and map printing, as well as large buildings for storing flat maps. Above

4608-591: The command of the Duke of Cumberland. Among Watson's assistants were William Roy , Paul Sandby and John Manson. The survey was produced at a scale of 1 inch to 1,000 yards (1:36,000) and included " the Duke of Cumberland's Map " (primarily by Watson and Roy), now held in the British Library . Roy later had an illustrious career in the Royal Engineers (RE), rising to the rank of General, and he

4704-559: The correspondence between a flat map and the round Earth is necessarily imperfect. At the South Pole , grid north conventionally points northwards along the Prime Meridian . Since the meridians converge at the poles, true east and west directions change rapidly in a condition similar to gimbal lock . Grid north solves this problem. Locations in a projected coordinate system, like any cartesian coordinate system, are measured and reported as easting/northing or ( x , y ) pairs. The pair

4800-563: The development of the railways added to pressure that resulted in the Ordnance Survey Act 1841 ( 4 & 5 Vict. c. 30). This granted a right to enter property for the purpose of the survey. Following a fire at its headquarters at the Tower of London in 1841 the Ordnance Survey relocated to a site in Southampton and was in disarray for several years, with arguments about which scales to use. Major-General Sir Henry James

4896-405: The direction of William Mudge , as other military matters took precedence. It took until 1823 to re-establish the relationship with the French survey made by Roy in 1787. By 1810, one-inch-to-the-mile maps of most of the south of England were completed, but they were withdrawn from sale between 1811 and 1816 because of security fears. By 1840, the one-inch survey had covered all of Wales and all but

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4992-522: The early 1940s, the OS produced many "restricted" versions of the County Series maps and other War Department sheets for War Office purposes, in a variety of large scales that included details of military significance such as dockyards, naval installations, fortifications and military camps. Apart from a brief period during the disarmament talks of the 1930s, these areas were left blank or incomplete on standard maps. The War Department 1:2500s, unlike

5088-416: The equator 500km west of the central meridian of the zone (the edge of the zone itself is just under 400km to the west). This has the desirable effect of making all coordinates within the zone positive values, being east and north of the origin. Because of this, they are often referred to as the easting and northing . Grid north ( GN ) is a navigational term referring to the direction northwards along

5184-570: The grid lines of a map projection . It is contrasted with true north (the direction of the North Pole ) and magnetic north (the direction in which a compass needle points). Many topographic maps , including those of the United States Geological Survey and Great Britain's Ordnance Survey , indicate the difference between grid north, true north, and magnetic north. The grid lines on Ordnance Survey maps divide

5280-419: The industrial areas were extensive office areas. The complex was notable for its concrete mural. Celestial , by sculptor Keith McCarter and the concrete elliptical paraboloid shell roof over the staff restaurant building. In 1995, the Ordnance Survey digitised the last of about 230,000 maps, making the United Kingdom the first country in the world to complete a programme of large-scale electronic mapping. By

5376-516: The information now being available in the AddressBase products – so as of 2020, MasterMap consists of Topography and Imagery. Pricing of licenses to OS MasterMap data depends on the total area requested, the layers licensed, the number of TOIDs in the layers, and the period in years of the data usage. OS MasterMap can be used to generate maps for a vast array of purposes and maps can be printed from OS MasterMap data with detail equivalent to

5472-438: The late 1990s technological developments had eliminated the need for vast areas for storing maps and for making printing plates by hand. Although there was a small computer section at the Ordnance Survey in the 1960s, the digitising programme had replaced the need for printing large-scale maps, while computer-to-plate technology (in the form of a single machine) had also rendered the photographic platemaking areas obsolete. Part of

5568-421: The latitude and longitude of the natural origin, the false northing and false easting, and an overall scale factor. Given the parameters associated with particular location or grin, the projection formulas for the transverse Mercator are a complex mix of algebraic and trigonometric functions. Every map projection has a natural origin , e.g., at which the ellipsoid and flat map surfaces coincide, at which point

5664-400: The latter was converted into a new conference centre in 2000, which was used for internal events and also made available for external organisations to hire. The Ordnance Survey became an Executive Agency in 1990, making the organisation independent of ministerial control. In 1999 the agency was designated a trading fund , required to cover its costs by charging for its products and to remit

5760-547: The leisure market. In 1920 O. G. S. Crawford was appointed Archaeology Officer and played a prominent role in developing the use of aerial photography to deepen understanding of archaeology. In 1922, devolution in Northern Ireland led to the creation of the Ordnance Survey of Northern Ireland (OSNI) and the independence of the Irish Free State led to the creation of the Ordnance Survey of Ireland , so

5856-409: The mile) for Land Valuation and Inland Revenue purposes: the increased scale was to provide space for annotations. About a quarter of these 1:1250s were marked "Partially revised 1912/13". In areas where there were no further 1:2500s, these partially revised "fifty inch" sheets represent the last large-scale revision (larger than six-inch) of the County Series. The County Series mapping was superseded by

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5952-453: 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

6048-738: The north of England to a scale of 1:2,500. In 1855, the Board of Ordnance was abolished and the Ordnance Survey was placed under the War Office together with the Topographical Survey and the Depot of Military Knowledge. Eventually in 1870 it was transferred to the Office of Works . The primary triangulation of the United Kingdom of Roy, Mudge and Yolland was completed by 1841, but was greatly improved by Alexander Ross Clarke who completed

6144-429: 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

6240-426: The one that Roy had used in 1784), and work began on mapping southern Great Britain using a 5 mi (8 km) baseline on Hounslow Heath that Roy himself had previously measured; it crosses the present Heathrow Airport . In 1991, Royal Mail marked the bicentenary by issuing a set of postage stamps featuring maps of the Kentish village of Hamstreet . In 1801, the first one-inch-to-the-mile (1:63,360 scale) map

6336-428: The organisation to move from a trading fund model to a government-owned limited company , with the move completed in April 2015. The organisation remains fully owned by the UK government and retains many of the features of a public organisation. In September 2015 the history of the Ordnance Survey was the subject of a BBC Four TV documentary entitled A Very British Map: The Ordnance Survey Story . On 10 June 2019

6432-467: The original Ordnance Survey pulled its coverage back to Great Britain. In 1935, the Davidson Committee was established to review the Ordnance Survey's future. The new Director General, Major-General Malcolm MacLeod , started the retriangulation of Great Britain , an immense task involving the erection of concrete triangulation pillars ("trig points") on prominent hilltops as infallible positions for theodolites. Each measurement made by theodolite during

6528-428: The printing of grids on maps by the U.S. Army Map Service (AMS) and other combatants. Initially, each theater of war was mapped in a custom projection with its own grid and coding system, but this resulted in confusion. This led to the development of the Universal Transverse Mercator coordinate system , possibly adopted from a system originally developed by the German Wehrmacht . To facilitate unambiguous reporting,

6624-417: The production of six-inch maps of Ireland was complete. This had led to a demand for similar treatment in England, and work was proceeding on extending the six-inch map to northern England, but only a three-inch scale for most of Scotland. When Colby retired, he recommended William Yolland as his successor, but he was considered too young and the less experienced Lewis Alexander Hall was appointed. After

6720-409: The projection formulas generate a coordinate of (0,0). To ensure that the northing and easting coordinates on a map are not negative (thus making measurement, communication, and computation easier), map projections may set up a false origin , specified in terms of false northing and false easting values, that offset the true origin. For example, in UTM, the origin of each northern zone is a point on

6816-447: The real church, independently of the actual size of the church. Grid references comprising larger numbers for greater precision could be determined using large-scale maps and an accurate Romer . This might be used in surveying but is not generally used for land navigating for walkers or cyclists, etc. The growing availability and decreasing cost of handheld GPS receivers enables determination of accurate grid references without needing

6912-410: The rest of Europe in preparation for its invasion . Until 1969, the Ordnance Survey largely remained at its Southampton city centre HQ and at temporary buildings in the suburb of Maybush nearby, when a new purpose-built headquarters was opened in Maybush adjacent to the wartime temporary buildings there. Some of the remaining buildings of the original Southampton city-centre site are now used as part of

7008-498: The retriangulation was repeated no fewer than 32 times. The Davidson Committee's final report set the Ordnance Survey on course for the 20th century. The metric national grid reference system was launched and a 1:25000-scale series of maps was introduced. The one-inch maps continued to be produced until the 1970s, when they were superseded by the 1:50000-scale series – as proposed by William Roy more than two centuries earlier. The Ordnance Survey had outgrown its site in

7104-752: The significant digits (3,4, and 5 in this case) are known to both parties. Alphanumeric encodings typically use codes to replace the most significant digits by partitioning the world up into large grid squares. For example, in the Military Grid Reference System , the above coordinate is in grid 11U (representing UTM Zone 11 5xxxxxx mN), and grid cell NS within that (representing the second digit 5xxxxxmE x6xxxxxm N), and as many remaining digits as are needed are reported, yielding an MGRS grid reference of 11U NS 949 361 (or 11U NS 9493 3617 or 11U NS 94934 36174). The Ordnance Survey National Grid (United Kingdom) and other national grid systems use similar approaches. In Ordnance Survey maps, each Easting and Northing grid line

7200-399: The six northernmost counties of England. Surveying was hard work. For instance, Major Thomas Colby , the longest-serving Director General of the Ordnance Survey, walked 586 mi (943 km) in 22 days on a reconnaissance in 1819. In 1824, Colby and most of his staff moved to Ireland to work on a six-inches-to-the-mile (1:10,560) valuation survey. The survey of Ireland, county by county,

7296-458: The six-inch standard was adopted in Great Britain for the un-surveyed northern counties and the 1:1056 scale also began to be adopted for urban surveys. Between 1842 and 1895, some 400 towns were mapped at 1:500 (126 inches), 1:528 (120 inches, "10 foot scale") or 1:1056 (60 inches), with the remaining towns mapped at 1:2500 (~25 inches). In 1855, the Treasury authorised funding for 1:2500 for rural areas and 1:500 for urban areas. The 1:500 scale

7392-427: 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

7488-405: 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

7584-554: 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

7680-477: The standard issue, were contoured . The de-classified sheets have now been deposited in some of the Copyright Libraries, helping to complete the map-picture of pre-Second World War Britain. From 1824, the OS began a 6-inch (1:10,560) survey of Ireland for taxation purposes but found this to be inadequate for urban areas and adopted the five-foot scale (1:1056) for Irish cities and towns. From 1840,

7776-720: 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

7872-422: 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

7968-524: The survey are to endeavour to obtain the correct orthography of the names of places by diligently consulting the best authorities within their reach. The name of each place is to be inserted as it is commonly spelt, in the first column of the name book and the various modes of spelling it used in books, writings &c. are to be inserted in the second column, with the authority placed in the third column opposite to each. Whilst these procedures generally produced excellent results, mistakes were made: for instance,

8064-479: The system created solely for Great Britain and its outlying islands (including 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

8160-647: The term is still common in some domains such as the military that encode coordinates as alphanumeric grid references . However, the term projected coordinate system has recently become predominant to clearly differentiate it from other types of spatial reference system . The term is used in international standards such as the EPSG and ISO 19111 (also published by the Open Geospatial Consortium as Abstract Specification 2), and in most geographic information system software. The map projection and

8256-467: The true central meridian at 117°W) and 5.6 million meters north of the equator . While such precise numbers are easy to store and calculate in GIS and other computer databases, they can be difficult for humans to remember and communicate. Thus, since the mid 20th century, there have been alternative encodings that shorten the numbers or convert the numbers into some form of alphanumeric string. For example,

8352-422: The two scales was completed by the 1890s, with a second edition completed in the 1890s and 1900s. From 1907 till the early 1940s, a third edition (or "second revision") was begun but never completed: only areas with significant changes on the ground were revised, many two or three times. Meanwhile, publication of the one-inch to the mile series for Great Britain was completed in 1891. From the late 19th century to

8448-587: 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

8544-548: Was begun in earnest in 1790 under Roy's supervision, when the Board of Ordnance (a predecessor of part of the modern Ministry of Defence ) began a national military survey starting with the south coast of England. Roy's birthplace near Carluke in South Lanarkshire is today marked by a memorial in the form of a large OS trig point . By 1791, the Board received the newer Ramsden theodolite (an improved successor to

8640-527: Was by then Director General, and he saw how photography could be used to make maps of various scales cheaply and easily. He developed and exploited photozincography , not only to reduce the costs of map production but also to publish facsimiles of nationally important manuscripts. Between 1861 and 1864, a facsimile of the Domesday Book was issued, county by county; and a facsimile of the Gough Map

8736-543: Was completed in 1846. The suspicions and tensions it caused in rural Ireland are the subject of Brian Friel 's play Translations . Colby was not only involved in the design of specialist measuring equipment. He also established a systematic collection of place names, and reorganised the map-making process to produce clear, accurate plans. Place names were recorded in "Name Books", a system first used in Ireland. The instructions for their use were: The persons employed on

8832-457: Was considered more 'rational' than 1:528 and became known as the "sanitary scale" since its primary purpose was to support establishment of mains sewerage and water supply. However, a review of the Ordnance Survey in 1892 found that sales of the 1:500 series maps were very poor and the Treasury declined to fund their continuing maintenance, declaring that any revision or new mapping at this scale must be self-financing. Very few towns and cities saw

8928-449: Was issued in 1870. From the 1840s, the Ordnance Survey concentrated on the Great Britain " County Series ", modelled on the earlier Ireland survey. A start was made on mapping the whole country, county by county, at six inches to the mile (1:10,560). In 1854, "twenty-five inch" maps were introduced with a scale of 1:2500 (25.344 inches to the mile) and the six inch maps were then based on these twenty-five inch maps. The first edition of

9024-457: Was largely responsible for the British share of the work in determining the relative positions of the French and British royal observatories. This work was the starting point of the Principal Triangulation of Great Britain (1783–1853), and led to the creation of the Ordnance Survey itself. Roy's technical skills and leadership set the high standard for which the Ordnance Survey became known. Work

9120-501: Was published, detailing the county of Kent , with Essex following shortly afterwards. The Kent map was published privately and stopped at the county border, while the Essex maps were published by the Ordnance Survey and ignored the county border, setting the trend for future Ordnance Survey maps. During the next 20 years, about a third of England and Wales was mapped at the same scale (see Principal Triangulation of Great Britain ) under

9216-670: Was unusual in that land registration on transfer of title was made compulsory there in 1900. The 1:1056 sheets were partially revised to provide a basis for HM Land Registry index maps and the OS mapped the whole London County Council area (at 1:1056) at national expense. Placenames from the second edition were used in 2016 by the GB1900 project to crowd-source an open-licensed gazetteer of Great Britain. From 1911 onwards – and mainly between 1911 and 1913 – the Ordnance Survey photo-enlarged many 1:2500 sheets covering built-up areas to 1:1250 (50.688 inches to

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