Christopher Somerville: Switch off the Sat Nav and put your best feet forward with our marvellous maps

That's the debate that is beginning to catch fire across the country, as Sat Nav sends drivers the wrong way down motorway ramps, up roads that were closed ages ago, and into lanes a slim cyclist would have a problem negotiating.

As a dedicated map-and-compass walker, but also a paid-up member of the 21st-century human race, I think a Sat Nav on a baffling car journey is a boon. Phone apps and Satmaps for walkers and cyclists – bring 'em on. Technology rocks. But it also sucks, if you don't bring common sense – and an Ordnance Survey 1:25,000 Explorer map – to the party.

There's nothing scary about an Explorer map, other than spreading it out bigger than a dining table and then having to get the damn thing folded up smaller than a place-mat once more.

And once you've mastered that secret (learning the concertina can help) and got it stowed in a transparent map case (a fiver at all good outdoor shops), what it is pretty much perfect at is showing you exactly where you are, and what's all around you – field walls, wood edges, barns, stony slopes, lanes, pubs.

It's great at suggesting where you might go next, whispering of a thousand places just out of sight that you could fall in love with. It tells you the means of getting there on foot along the fantastic cat's cradle of footpaths and bridleways, cycle tracks, permissive paths and ancient packhorse lanes, our great unsung national birthright, which are all shown on the map by various kinds of dotted and dashed green lines.

And it lets you know how many miles (or kilometres, if you're French) you'll be walking – there's a handy scale at the bottom. A mile on the map is about as long as your little finger (well, mine, anyway).

Quite frankly, that's just about all a walker needs to know. Everywhere it's green and dotted, you have the right to go. Everywhere the brown spidery contour lines move close together, it's steep. Where they spread out and there's lots of white between them, it's flatter. Choosing a walk couldn't be simpler. Just find a little blue beer-mug symbol that shows the presence of a pub.

Now trace out with your finger a circle of five or six little fingers' length that brings you back to the pub, keeping as much to the green dots and dashes as you can, and going as steep or flat as you like. Bingo – a nice morning or afternoon's walk, and a pie and a pint at the end of it.

Of course, you can cut out the pub part, and just start anywhere. But most walkers I know wouldn't care for that sort of talk at all.

I'll actually try that experiment now. Here's OS Explorer

298, "Nidderdale". I've opened it up, and now I'll stab my finger down at random. Summerbridge, I've hit, between Ripley and Pateley Bridge. There's a blue mug there; that's base camp secured.

Let's see – Dacre Banks, Heyshaw, Skrikes Farm (nice name), Baylis Camp, Bark Cabin Wood, Lead Wath Wood, Summerbridge. About eight little fingers – eight miles. Pull up "Summerbridge, pub" on Google... the Flying Dutchman.

Job done. I've never walked in the Summerbridge area, but everything I need to give me confidence that I'll have a great day out on the hoof is right there in front of me on my kitchen table. And the Explorer gives me a fabulous bonus, too, with its sheer size.

It covers 200 square miles of prime North Yorkshire countryside. It tells me about literally dozens of other walks I can do within a few minutes' drive of Summerbridge. And it relates the overall geography of the area, so that I notice how the lake-like reservoirs of Scar House and Gouthwaite use the lie of the land to catch and pass on the waters of the River Nidd.

I can see, spreading out from the lips of Nidderdale, the great empty moors of Masham and Fountains Earth, of Ramsgill and Raygill House, tinted yellow to show they are access land open to all, with their gutters and gills and springs, their ancient crosses and standing stones, and their mile upon mile of moor roads that are mine to follow if I please. And I do please.

There's nothing more boring than a self-righteous Luddite banging on about how terrible modern technology is. I don't want to tread anywhere near that. But let's not seal ourselves off from the incomparable delights of the real world out there.

Let's hear it for looking about us in wonder and delight with our five senses all turned up to 11, for charting our explorations by landmarks as well as by Sat Nav bleeps, and, above all, for the OS Explorer map, the lively-minded walker's and wanderer's boon companion, teacher and friend in need, all yours for under a tenner.

Christopher Somerville's UK geography primer for grown-ups, Never Eat Shredded Wheat – the Geography we've lost and how to find it again, is published by Hodder & Stoughton, price 12.99.