Camping with grace, Thomas de Dorlodot and Ferdinand Van Schelven are paragliding the length of the South Island.

If adventurer Tom de Dorlodot had a day job in New Zealand, his office would be hanging beneath a paraglider, thousands of metres in the air above the Southern Alps.

"It's the ultimate freedom. It's a beautiful way to travel, because you're not disturbing anything. Even the birds come and fly with."

The Belgian man and his Dutch friend Ferdinand van Schelven are professional paragliders who have landed in Nelson after a month-long adventure through the Southern Alps.

THOMAS DE DORLODOT AERIAL EXPLORERS: Ferdinand Van Schelven and Thomas de Doorlot.

Their sport is vol-bivouac, literally "fly-camping" in French, which is riding a current of popularity overseas and could, according to the Red Bull-sponsored pilots, take off big in New Zealand.

Starting on a mountain peak in Otago and ending on a beach near Nelson, the pair have paraglided and walked nearly the length of the South Island, carrying with them just a parachute, some camping gear, and a pair of quickly worn-out walking boots.

"Either you walk, and you have to carry your paraglider; or you fly, and your paraglider carries you," de Dorlodot said, describing their 800km trip up the island.

Carrying less than 20kg of gear, de Dorlodot and van Schelven took 27 days to traverse the backbone of the South Island, from Te Anau to Nelson. Along the way they fished for trout in tranquil back country streams, drank glacier water fresh from the source, and soared with the birds above Aoraki/Mt Cook.

It was "a beautiful idea" coming to New Zealand, de Dorlodot said. Every morning the pair would wake, climb 2000-odd metres up a mountain, and jump off with their paragliders.

Once airborne their trick was to traverse the alps from above, flying as far as they could on thermal currents and friendly breezes. Eventually they would land, sleep in a hut or wrapped in the warmth of their 'chutes, then repeat the process.

"On a good day, if you don't have wind coming into the face and you can fly fast, you can cover up to 100 kilometres," de Dorlodot said. "Some days we fly 40 kilometres over two mountain passes that would have been four days of walking, and we do it in hours.

"When you know you have 100km to walk if you land, it's quite good motivation for flying and pushing yourself a little bit."

Unable to glide into Air Nelson airspace, they walked the final 75km north from St Arnaud.

"We said the stop was the sea. When we came in between Richmond and Nelson we arrived at the beach and said that's it," de Dorlodot said.

"That's a pretty good feeling, knowing you have crossed the whole thing with just a pair of shoes and a paraglider."

De Dorlodot and van Schelven are training for the "vol-biv" world championship - the RedBull X-Alps mountain race between Saltzburg, Austria and Monaco - in July. Competitors travel by air or by foot through 800km of hostile European alpine terrain.

New Zealand had been sweet for finding unique take-off locations, de Dorlodot said, as nearly every peak they jumped off was a world-first. He said Nelson, with its surrounding mountains and prevalent sea-breezes, could become a centre for the growing sport, which is primarily based out of Europe and throughout the sub-Asian ranges.

Van Schelven had flown in Nelson five years ago, when he dominated a competition, winning five-out-of-six "vol-biv" events.

When de Dorlodot isn't flying he is thinking about it. His RedBull sponsored Search project sends him around the world for a living, looking for the best places to vol-biv. Last year he crossed the length of Africa, soaring over the pyramids and Victoria Falls. His proudest achievement was gliding at 7200m to within 1km of the K2 summit in Pakistan.

"I think maybe it would have been possible to soar up. But, I didn't dare to. It has never been done. I was alone there, even a little scared, so I kept a respectful distance."