'Turn left towards Petworth," she instructs in her smoky tones. I nod, brake, and turn left towards Petworth. I don't know where I'd be without Sophie, but it wouldn't be where I was supposed to be. I find the world a maze, its streets a knotty tangle. When right is right, every instinct tugs me left; a trip from A to B invariably takes in several other letters of the alphabet. I pull up on to a grassy bank overlooking the South Downs. Five minutes early. I give Sophie an appreciative pat and then shove her into the glove compartment.
My helpless reliance on GPS technology would offend the sensibilities of Tristan Gooley. The self-styled "Natural Navigator" devotes his life to travelling without gadgets or web-based route-planners or frantic calls to friends – indeed, for three years he's run courses on the subject.
Our meeting today is the equivalent of that between a mole and a homing pigeon. "Why don't I simply use a satnav?" Tristan asks rhetorically, as I shuffle uncomfortably and avoid his eye. "Because life's not just about necessity. Natural navigation offers the chance to reconnect with our surroundings."
Within a minute we're reading one of nature's signposts. It's an ash tree. "What do you notice?" challenges Tristan. I stare blankly. "Look more closely," he encourages, and we stick our faces through leaves and twigs. "Do you see how the branches are different on that half of the trunk?" I do – they are thicker and longer – it's like a tree that visits the gym but only works on its left side. "This tree throws out leaves for three months a year to feed on sunlight. The sun's at its strongest in the south and so the tree has developed more powerfully in that direction."
Tristan's had adventures that would make a schoolboy swoon. Who else has crossed the Atlantic single-handed by both air and sea? Nobody on Earth. But he's always been more fascinated by the choosing of the path than the monsters found along it. The moment that most thrilled him during his daring solo flight was spotting a cloud and correctly deducing from its brightness that he was travelling north-east. It's not very Indiana Jones. No, Tristan's the thinking man's explorer. He has studied sailors in the Pacific who are guided by the stars, and watched nomads in the desert point to Mecca in a flash. He's learnt that the landscape contains its own map; we have just forgotten how to read it.
We strike out along the South Downs Way, a white stripe over the countryside's gentle swell. Tristan looks up to the clouds smeared on the sky. "I once navigated through London using clouds. I nearly got run over, but I didn't get lost." As skylarks burst with song above pink-tipped wheat fields, he unrolls nature's map before me. I discover that tracks are generally a shade darker at their southern edges and that the delicate blue flowers of the germander speedwell only line the northern sides. Storms usually follow the direction of prevailing winds, so toppled trees in a wooded glade are like needles on a compass.
But beware nature's traps. Most mosses like moisture but this golden lichen bucks the trend; undulating land can cause wind to change course by up to 50 degrees. See that gorse bush? Tristan believes its yellow flowers grow lower on branches to the south, although he'll need to test his theory further. On he moves, relentless, like a bloodhound.
And then he fires a question that hits me like iced water. "Your car's to the north; which way is that?" My breath quickens sharply. Calm down. Think. Assess the surroundings. There's an oak over there and it's heavier on one side – that's south, it must be! But – wait – tyre marks. This path is used by tractors and they could be altering the tree's shape as they pass. Ignore that clue. Aha, what's this? A dark smudge of moss on a fence post – now we're in business – it might point north. It's good, but I need something more ... And there it is. You beauty! That windswept tree on the horizon – the one that looks like it's been brushed by the hand of a giant – has clearly been affected by exposure to south-westerlies. The moss wasn't lying. "North!" I gesture excitedly, and Tristan smiles. "Spot on."
There's a mystical quality to natural navigation; its approach is closer in spirit to St John's Gospel – or the novels of Dan Brown – than to the macho world view of outdoorsy types such as Bear Grylls who see nature as something to survive. At its heart is a sense of dislocation, an awareness of lost knowledge. There are codes to be cracked and signs to be read, and through the cracking and the reading comes fulfilment. Interpreting the landscape isn't a means to an end – it's an end in itself. Tristan isn't just teaching about trees – he's removing logs from people's eyes. As I climb into my car, I leave the glove compartment closed. It's time to face life without Sophie.
Tristan Gooley (naturalnavigator.com) runs classroom-based, one-day courses on "natural navigation" in London and in West Sussex. He offers bespoke outdoor courses, but the three-hour Weekday Whirlwind option on the South Downs is an ideal introduction and costs £115.
Tristan's new book, The Natural Explorer: Understanding Your Landscape, is published by Sceptre on Thursday (£16.99)