The Ordnance Survey, as we know it now, was founded in June 1791, but the history of Ordnance Survey maps is older than that, the initial idea for an official mapping system being much older than that. In fact there was a survey of Scotland done between 1747 and 1755 which measured the country at a level of detail of one inch to 1000 yards, thus the history of Ordnance Survey maps could be considered to have started then. This survey still survives now. It was done by an army officer, Col. David Watson, and the Engineers of the Board of Ordnance, which at the time was a separate board. This was the first official Government survey of a substantial area of Great Britain, and is widely credited as inspiring further official surveys over the following decades.
The Royal Societies of London and Paris decided, in 1783, to reach agreements over the relative positions of observatories in those cities, and to connect them together through triangulation. To do this, they needed to have some detailed surveys carried out, and it was that decision which was a landmark event for the growth of the survey system. The triangulation was completed by 1790, but this did not mark the end of the work because the third Duke of Richmond was a fan of the work, and authorised the Ordnance to continue it, with Ã‚Â£373.14s of UK funds. The authorisation took place on the 21 June 1791, and that is now taken to be the official formation date of the Ordnance Survey.
Over the next few years there were several military maps made, because Britain was at war with France and those maps were needed for its defence. The war ended in 1815, and by that point large swathes of England had been mapped Ã¢Â€Â“ from Birmingham southwards. Early maps were just six inches to a mile, but that scale was controversial. Some opponents preferred24 inches to a mile, while others were calling for one or three inch scales. In the 1850s and 1860s, such a scale would have been a rather ambitious attempt. The treasury wanted to push for a 24 inch scale because it was more cost effective. In the end, there was a 1:25000 project (25.344 inches per mile) begun, with towns that were willing to pay to have more detailed maps made having the opportunity to do so.
Thus an aggressive remapping project began, and it was finished well ahead of schedule. The government had expected that the work would not be done until 1900, but it was finished in 1888, with the exception of the towns that wanted much more detailed maps to be done.
Improvements in technology, of course, never cease. Experiments with digital maps began in 1969. The process of remaking digital maps however proved slow, and the government decided to contract the work out in the 1970s. The conversion of all the existing maps to a digital format was finished in the mid 1990’s, twenty years before it would have been done had the work all been done in-house. In 1990, the Ordnance Survey became an Executive Agency, and in 1999 it became a government Trading Fund, and a profitable one at that.
For more information on digital maps see useful resource