Ordnance Survey

England was squeezed between rebellion in Scotland and war with France when King George II commissioned a military survey of the Scottish highlands in 1746. The job fell to William Roy, a far-sighted young engineer who understood the strategic importance of accurate maps.

His vision of a national military survey wasn't implemented until after his death in 1790. By then Europe was in turmoil, and there were real fears that the French Revolution might sweep across the English Channel. Realising the danger, the government ordered its defence ministry – the Board of Ordnance – to begin a survey of England's vulnerable southern coasts.


Military mapping

It was back in 1791 that the Government realised that in order to plan adequate defences to repel any invasion, the South Coast of England needed to be comprehensively and accurately mapped. That historic decision led to the mapping the whole country in detail.

Surveyors began mapping southern Britain from a baseline that Roy himself had measured several years earlier. The first one-inch map of Kent was published in 1801. Within twenty years about a third of England and Wales had been mapped at the one-inch scale.


A taxing business

In the mid-1830s, the demands of the Tithe Commutation Act provoked calls for detailed six-inch surveys in England and Wales. In 1841, the Ordnance Survey Act gave surveyors a legal right to 'enter into and upon any land' for survey purposes.

The scene was now set for two decades of wrangling over scales. The issue was settled piecemeal until, by 1863, scales of six inches and twenty-five inches to the mile had been approved for mountain and moorland, and rural areas respectively. The one-inch map was retained, and detailed plans at as much as ten feet to the mile were introduced for built-up areas.


War and peace

By 1895 the twenty-five inch survey was complete. As Britain entered the First World War, surveyors, draughtsmen and printers from Ordnance Survey were posted overseas. Working alongside the troops, surveyors plotted the lines of trenches and, for the first time, aerial photography was used to capture survey information.

After the war, a professional artist was appointed to produce eye-catching covers for the one-inch maps, but behind their bright new covers, the maps were increasingly out of date.


A landmark review

Matters came to a head in 1935, and the Davidson Committee was established to review Ordnance Survey's future. That same year the retriangulation of Great Britain was launched. Surveyors began an Olympian task, building the now familiar concrete triangulation pillars on remote hilltops throughout Britain.

The National Grid reference system was introduced, using the metre as its measurement. An experimental new 1:25,000 scale map was launched, leaving only the one-inch unscathed. It was almost forty years before this popular map was superseded by the 1:50,000 scale series, first proposed by William Roy more than two centuries earlier.

After the war, aerial survey helped speed up the new continuous revision strategy, and up-to-date drawing and printing techniques were introduced and in 1973 the first computerised large-scale maps appeared.


E-volution

Ordnance Survey digitised the last of some 230,000 maps in 1995, making Britain the first country in the world to complete a programme of large-scale electronic mapping. Electronic data now accounts for some 80% of Ordnance Survey's turnover. Independent estimates show that the national mapping agency's data now underpins up to £136 billion-worth of economic activity in Britain – everything from crime-fighting and conservation to marketing and mobile phones.