Maps have been created since ancient times but often left much to be desired in terms of scale and accuracy.

And if you're planning a military campaign, scale and accuracy could make the difference between victory and defeat.

What would later become Ordnance Survey has been producing maps for 225 years, since Wiliam Roy made a survey of the Scottish Highlands in 1747.

But Kent was the subject of the very first accurately triangulated map produced under the name Ordnance Survey, and it was all down to the fear of French invasion.

In the Georgian period, the French Revolution threw France into turmoil, making Europe increasingly nervous.

In 1799 the new republic was under the control of ambitious general Napolean Bonaparte, who promptly invaded or annexed several of France's European neighbours.

With the prospect of invasion looming, the British government orderedits defence ministry of the time - the Board of Ordnance - to start mapping the south coast.

This led to the first one-inch-to-the-mile Ordnance Survey map being published in 1801.

It was decided Kent, as England’s most south-easterly county, was most vulnerable to French invasion.

The military intentions of these early maps was clear. They featured elaborate hill shading and attention to communication routes, but most importantly, they were accurate.

This was thanks to a system called triangulation, first developed by the ancient Greeks, which involves dividing an area into triangles to determine a location based on the angles of each corner.

Place names often proved difficult as locals could argue over what name was actually correct.

Eventually the Name Book system was put in place.

Variations of all proper names such as rivers and hills, as well as towns, were recorded in a series of books and from this selection the most authoritative was chosen for publication.

These early Ordnance Survey maps were avaialbe to the public, either from the Board of Ordnance headquarters in the Tower of London, or from William Faden, a map seller at Charing Cross.

But they weren't cheap; at three guineas (£3 3s) per county survey, one map cost between one and three weeks’ wages for the average person.

Part of their appeal was they offered a bird’s eye view of the landscape – until then the privilege of very few hot air balloonists.

Four years after the completion of the Kent map, a map of Essex followed.

Within 20 years, about a third of England and Wales had been mapped at the one inch scale under the direction of William Mudge.

It was thought that 50 years would be long enough to map the country, but the entire first series of maps wasn’t published until 1870.

This year marks the 225 anniversary of Ordnance Survey, which continues to provide mapping services for a number of organisations worldwide.

But the modern products tend to be based on satellite data rather than the ancient methods used to produce the first maps.