Saturday, August 18, 2012

Ordnance Surveys and Family History

Ordnance Survey- noun, the official map making body of the British or Irish Government

Map of Ely Cambridgeshire Wikipedia

"I am told there are people who do not care for maps, and I find it hard to believe."  Robert Louis Stevenson, Treasure Island.

Maps are an extremely important resource for family historians. They allow us to place our ancestors into the geographical context of their lives. Old maps are also very useful for assisting us to find place names which may longer exist. This post, though, is not about maps in general, but rather, it ascribes to the specific maps which marked the coming of age of cartography in Great Britain -  Ordnance Survey maps. These maps were the first accurately measured and scaled maps to cover the entirety of Britain. Today the geographical data on these maps serves an enormous audience, which includes, defence forces, local and national government departments, architects, engineers and family historians.
"Ordnance Surveys intimately trace the course of all the roads, national trails, minor footpaths, bridleways, power cables, becks, gills, streams, brooks, and field boundaries that bisect a landscape of miniature woods, speckled scree slopes and orange contour lines...." "...before the Ordnance Survey map was created, Britain was represented by a mosaic of county and military surveys of variable accuracy, content and scale..."    Map of a Nation,  [Rachel Hewitt, London Granta, 2010]


The Office of Ordnance in Britain, dated as far back as the 14th century. Attached to the Royal Arsenal and located at the Tower of London, this body was responsible for overseeing the Monarch's armaments, castles and arsenals. In 1518, the Office of Ordnance became known as The Board of Ordnance, and although military in nature, was a body, independent of the Army. From the late 17th century, map making was an important function of the Board of Ordnance.

If you want to understand today, you have to look into the past." Pearl Buck

An historic decision made in June of 1791, by the British Board of Ordnance (the precursor of the Ministry of Defence), precipitated the first detailed mapping of Great Britain and was the agent for the interesting name Ordnance Survey.  Although this date is usually accepted as the founding date for the First Series of Ordnance Survey maps, the path which led to its foundation began earlier. The origins of the Ordnance Survey date back to earlier military surveying of Scotland following difficulties experienced during the Jacobite Uprisings (1745-6), due to extremely ineffective maps of the Scottish Highlands. Royalist troops were severely hindered by the inconsistencies and deficiencies of available maps. Maps were marked with variances of names, places names were overlooked altogether, and no maps afforded  a factual outline of  the  inaccessible mountains, rivers and lochs of the Scottish Highlands.  In 1766, proposals were made to the Government for the first official scaled survey of Scotland as well as a 'general military map of England', suggesting a scale of 2 inches to the mile.

It had become obvious that although Britain possessed national maps, most were highly decorated, beautifully coloured, works of art. Early maps were rarely produced by actual measurement of the ground, owing to the lack of measuring instruments, and although beautiful to gaze upon, were neither dependable nor accurate.  Tithe maps, created in the early to mid 1800's showed details related to landowners and dwellings, as did Valuation Office Surveys and National Farm Surveys. These maps, although extremely valuable sources  for family historians, are fairly unreliable, being inconsistent as well as having no accurate measurement nor significantly, scale.

A Map of England depicting it in the Saxon times, John Speed, 1670

The real foundations were laid for the Ordnance Survey maps in 1783-4, when the Royal Societies of Paris and London set about resolving a controversy,  regarding the accuracy of the sites of the astronomical observatories in these two cities. They embarked on a project to position the cities by means of a system of triangulation ( measuring distance and determining locations, by measuring angles from determined points). Triangulation remained the main mechanism of surveying until replaced by modern satellite positioning systems. In 1784, the triangulation of south-east England from a base line on Hounslow Heath was commenced. Although the Paris-London triangulation, completed in 1790,  was a civil pursuit,  responsibility for the enterprise was assigned to Major-General William Roy ( 1726-1790), who was assisted by the Royal Artillery and this surveying was the basis for the first Ordnance Survey.

The purchase by the Board of Ordnance of a new surveying instrument called the Great (or 36 inch) Ramsden Theodolite, and the threat of French invasion, instigated a national military survey, in 1791, which began with the mapping of south east Britain using the baseline that Roy had measured. So commenced one of the world's most systematic and thorough mapping agencies. Britain's national mapping agency, the Ordnance Survey, or  OS thus, emanated from a history of military maps. Its history encapsulates political revolutions, wars, and regional divisions which have changed both physically, in character and in identity.

The Great Ramdsen Thoedolite, a precise instrument for measuring angles in the horizontal and vertical planes.

The first official map produced by the Ordnance Survey was published in 1801 by William Fadden. The detailed one inch to one mile scaled map was of the county of Kent. A map of Essex followed, after which all of Britain and Ireland were surveyed and mapped. The Ordnance Survey became Britain's national mapping agency and has remained at the forefront of mapping ever since. Over the years since 1791, the Ordnance Survey has updated and revised its enormous collection of survey maps. The OS was responsible for formulating the national grid reference system which references  locations within the British Isles.   Ordnance Survey maps today are considered to be  the hitchhikers guide to the landscape of Great Britain and the immense digital data base of the OS, fills the screens of our 'satnavs'. From the time that adventurous mapmakers, trekked the countryside of Britain, bearing the great heavy theodolites on their excursions, to today's government department which generates web mapping services whose geographic services benefit the community as a whole, the Ordnance Survey has dominated the terrain of mapping.


Ordnance Survey maps are a fundamental resource for family historians. Maps produced by the Ordnance Survey are amongst the best in quality in the world. The OS has produced maps of Britain in ancient times, Roman times and maps relating to Britain during the Medieval Era. It has a vast collection of photographs which span many years of surveys and its collection of maps over time are a unique record of  Britain's metamorphosis, as boundaries of civil parishes and government divisions of counties and place names altered throughout the years.

An Ordnance Survey map


The National Archives UK (TNA),  [>Records ] has excellent information about the Ordnance Survey, and retains a number of Ordnance Survey maps in their holdings.
The Ordnance Survey hosts its own website,  [ ].  Since April of 2010, the OS has offered a wide spectrum of mapping data, including, OS getamap ( an online application for maps from Ordnance Survey), and an educational category which is well worth exploring. The OS site, explains in depth how to choose the correct map to suit your purpose (eg  you can find out which scale map  is most useful to you as a family historian). You will need to register with this site but if you are searching for reliable Ordnance maps as a family history resource, this website is well worth visiting. The OS website also hosts an informative blog which is worth following if you use maps as family history sources. Below, I have included an example of one of my own OS searches for Cramlington in Northumberland which was the birth place of my great great grandmother, Hannah Tait GAIR, in 1846.

Search page on the OS website

My search results for 'Cramlington'

The detailed OS map of Cramlington I found.

The OS website offers maps in different scales to suit assorted purposes and offers advice on how to choose the map most appropriate for you.

OS map at 1:10 000 scale showing roads, road names and major buildings.
An example of OS range of map scales.
On the above maps you can click on each example to view a larger version to understand the different scales and uses of the OS maps.
The Ordnance Survey website explains in detail the national grid, and presents a fascinating interactive guide to this information. To view this, requires Adobe Flash player plug in.

The National Grid.

Old Maps UK    [ ] is an online repository of old maps which includes Ordnance Survey maps. Amongst other maps you can search for Ordnance Survey County Series and Ordnance Survey Town Plans. This site is very user friendly and a search is easily performed. In the example below, I searched for the town of Long Houghton, in Northumberland, where my fourth great grandfather, Roger GAIR was born in 1782.

My first search result showing the location of Long Houghton in Northumberland.

A closer inspection of Long Houghton.

Using Maps in Genealogy    [  ] is a an excellent website, and most helpful to use as a map resource. This site explains how to use maps in your family history research.

Map from the Using Maps in genealogy Website.  provides many pertinent links to Ordnance Survey maps.

A Vision of Britain Through Time  [  ] is an excellent website which includes a searchable facility for finding First Series Ordnance Survey maps as well as newer Ordnance Survey maps. Once a map has been found for the location you are researching, this website offers  an historical description of the place, taken from local and national gazetteers.

Map and historical description of Hougham, Lincolnshire, where I can trace my Morley family back to 1633.


  1. Thoroughly researched and interesting post on a topic which is so invaluable to family history. One of my fondest memories of my last trip to the UK was meeting up with a second cousin in Wandsworth and poring over old O/S Maps of the area together. x

  2. Ditto to Deb's comment.

    You have given us another fabulous guide.