From map to mapping legend- A history of Ordnance Survey

This article was first written for the Mountain Training Association after a Ted Talk CPD session in 2022. 

Speak to any hiker from the UK or Ireland about maps and more than likely the name of one of our most famous organisations will be mentioned, Ordnance Survey (OS). Be it a paper map or on their phone, OS remains the best friend to everybody heading into the outdoors. Despite its prominence in our map culture, the history of OS mapping only goes back a short distance in time. Before the renaissance, mapping was not used as we think of it today but maps were instead a symbol of social status, obtainable to only those who were wealthy and with influence. While maps were used in a military context, these were often very unreliable or of an unusable scale by today’s standards.

The Great Map Begins

By the end of the Jacobite Rebellion in 1745, the Royalist forces had encountered severe issues from the lack of effective mapping. The best mapping available was at a staggering scale of 1 inch to 13.5 miles (or 1: 855,360!) proving to be woefully inadequate for the Army’s needs. In order to help with the crushing of future rebellions it was decided that Scotland needed to be mapped. The Board of Ordnance Survey tasked William Roy, a young surveyor, with the mapping of the entirety of Scotland, work which would later be more commonly known as the Great Map.

Initially, Roy was entirely on his own but as the project developed, more labour was made available to help complete this monumental task. The methodology involved taking a bearing using surveying compasses to key landmarks with lengths of chains up to 50 feet long used to measure distances before being sketched. This painstakingly slow process took 7 long years but his maps at 1:36,000 scale provided the accuracy required and has since become the basis of our mapping today.

Moving inwards

As a result of his excellent work, Roy would soon realise the need for mapping of the whole of the country. After joining the army and achieving the rank of General, he would regularly push for this nation to be mapped. However, it would take the threat of invasion from Emperor Napoleon before this idea was taken seriously. This threat lead to the mapping of the whole of the South Coast, leading to the creation of Ordnance Survey in 1791 to achieve such a goal.

As the work continued, the need to map the rest of the country became apparent so, with the use of the famous theodolite, accurate mapping was a real possibility. OS would also quickly realise there was money to be made and sold their first map in 1801. This was the map of Kent sold for £3 & 3 Shillings equating to approximately 3 weeks’ wages for a basic labourer at the time; this map would now cost £138.83 in today’s money! To map the whole country would prove to be a 70-year long project and while sadly Roy would not live to see his dream achieved, the achievement would echo through the decades to come.

Call to defend

At its heart, OS remained a military organisation, so when Britain entered the World Wars, OS would stand up to serve. In The Great War, OS would literally enter the trenches to survey and create detailed maps at a rapid pace. In 1918 alone Ordnance Survey reported they were sending on average 25900 maps globally per day! OS would not only produce maps but also lead the development of Aerial Surveillance. This allowed for the creation of very accurate mapping to be available to the Armed Forces, a task they still assist with today. By the end of the war they would have produced a total of 20 million maps for the British Armed Forces, however this was achieved with the loss of 37 OS workers’ lives.

World War 2 would see Ordnance Survey, once again, answer the country’s call. Their task this time made much more arduous with the bombing and destruction of OS Headquarters during the November 1940 Blitz. This resulted in the organisation being scattered throughout the country so they could continue to operate despite the Blitz. They would only come back together in Southampton in 1969.

Despite these problems during WW2, including the loss of 56 lives, OS would continue to prove their value to the Armed Forces. For D-Day and the Normandy Campaign, it would go on to produce 342 million maps for the Armed Forces, of which 120 million were used for D-Day and the Normandy campaign alone!

Dawn of the Modern OS

Perhaps one of the most recognised parts of Ordnance Survey would go on to be created during the last half of the 20th Century, The British National Grid. By the 1930s, the original work of mapping the nation was beginning to show its age with many of the maps heavily out of date. The decision was made for the country to be remapped, however many of the original points used to measure were either lost or damaged beyond use.

To help overcome this, it would lead to one of the most iconic sights on the ground for any hiker, the Triangulation Pillar, known commonly known as the trig point. Using 6500 of these points, what would become known as the great triangulation, the country would be completely remapped with a new coordinate system, still in use today. This would also lead to the creation of the iconic 1:25,000 scale. Due to the use of satellites in modern mapping, these trig points are now no longer used for their intended purpose. They have remained though as clear features on the ground which can be used for navigation and are done by many a hiker today.

Today and the future

As the end of the 20th century approached, OS would finally change into the organisation we know it as today.  In 1983, OS finally moved away from its military links and became a fully civilian organisation. This change of ownership did not blunt its ability to evolve; for example, the OS enabled the UK to be the first country in the world to digitise its maps, with 230,000 maps uploaded. It remains one of OS most used products. In 2022, OS is still a highly respected institution both in the UK and abroad, so much so they are now assisting in the mapping of Australia!  From an organisation that originally began with men using compasses, chains and pencils to an organisation with 600,000 people using their products a week, that’s quite a legacy!