Making maps
We sent CW’s budding cartographer into the nerve centre of the Ordnance Survey to rumble the secrets of the world’s greatest mapmakers…
IDON’T KNOW WHERE I’d be without my stash of Ordnance Survey maps. No, literally: I’d be lost without them. Yes, the pun is groanworthy, but I’m sure it’s a sentiment you share. I doubt I’m the only walker with a special place in my heart for the trusty OS Explorer map. They cover every corner of the British countryside in meticulous detail and are indispensable when it comes to discovering it on foot.
I remember my fifirst OS map: 148 ‘Maidstone & the Medway Towns.’ It was 2003 and the Ordnance Survey gave 750,000 schoolchildren a free map of their local area. But even before then I was fanatical about maps, beginning (as I’m sure many of us did as young ’uns), by scribbling treasure maps of the local park. Before long I’d moved on to mapping make-believe towns and villages. My nerdy hobby grew to new extremes when I even began to copy the Ordnance Survey’s trademark style ( which I wrote about back in January’s issue). A glittering career as a cartographer beckoned, but it wasn’t to be. Cartography’s loss turned out to be journalism’s affliction. But this meant that when the Ordnance Survey invited Country Walking to their Southampton HQ, I was fifirst in the queue…
MODERN CARTOGRAPHY
If I was expecting ranks of draughtsman painstakingly drawing every sheet by hand, then I was to be disappointed. Similarly, in the field, you’re unlikely to see anyone lugging around a theodolite between trig points these days. Like painting the Forth Bridge, mapping Britain is a never-ending task, and today’s Ordnance Survey cartographers use the latest in digital technology to build upon centuries of surveying and map making.
On the ground, a dedicated team of 240 surveyors is constantly updating a master map of Britain. Nowadays their work involves lasers and location positioning, using a network of GNSS (Global Navigation Satellite System) base stations – the modern successors of the trig point. The data is uploaded wirelessly, but just in case technology fails, surveyors still carry a tape measure and optical square as backup. Meanwhile, high in the sky, the Ordnance Survey’s own aeroplanes photograph the ground in amazing detail, using a camera with a whopping 196 megapixels. LIDAR laser beams enable surveyors to map it in 3D. These images are especially vital for the team mapping Britain’s ever-changing coastline, using 3D glasses to trace our shifting shores with absolute precision.
The human landscape – towns and roads – is always evolving too. With every new edition of Landranger and Explorer, there are changes to make, from bridges to bypasses.
Cartographers like Chris Kirchel work from the master map to create the leisure maps we know and love. With so many features, symbols and names to squeeze in, it’s a challenge to make sure the maps are both accurate and easy to read. So cartographers will ‘generalise’ features (simplify their outline) so they’re clear to see on the map.
On a normal day Chris can be rerouting roads and footpaths, planting forests and filling new reservoirs – all from the comfort of his desk!
It was an eye-opening experience: a mind- bogglingly complex process being handled quietly and calmly in an offiffice building like any other, somewhere in Hampshire. But before I left, there was one urban myth I was eager to clear up. In some circles, you might hear it said that the OS makes small but inconsequential errors as a way to protect their copyright; i.e, to trap copyright thieves into reproducing these errors and thus give themselves away.
But Chris assured me this isn’t so: “We never knowingly include any errors.” Accuracy is a cornerstone of what the Ordnance Survey do, and without it navigating the British countryside for pleasure would be a lot more diffifficult.