A basic definition of a world circumnavigation would be a route which covers at least a great circle, and in particular one which passes through at least one pair of points antipodal to each other. The center of a great circle is the same as that of the earth. For example, the longitudes are on great circles, and the Equator is the latitude which defines the longest great circle given the earth's shape. Other lines of latitude which are shorter are not great circles, because their centers do not match that of the Earth. Great circles divide the earth into two equal hemispheres.

The corollaries to all of the above descriptions are that a true circumnavigation route should:

• cross the Equator at a minimum of two points,
• touch at least one pair of antipodes,
• likely travel a distance that is equal to or more than the length of the Equator,
• make an honest effort to approximate a great circle,
• show equal effort in two opposite hemispheres respectively.

Six Summits Project will achieve a human powered circumnavigation:

Precedent - Surface Travel (human powered): Steven Strange from England holds the current Guinness record certificate for a "circumnavigation by bicycle." Steven has the rules for circumnavigation by bicycle spelled out on his site which include reaching a pair of antipodes. Steven started his bicycle ride on May 9, 2004 in Vancouver and 276 days later, finished his circumnavigation at the same place on February 13, 2005. Steven took plane rides across the oceans.

Another British man Alastair Humphreys recently completed a unique circumnavigation journey. Alastair crossed the oceans by boating, and he bicycled while on land. By the time that he had returned back to İstanbul in September 2005 closing the knot, he had covered 69,000 km. Alastair chose to bicycle another 3,000 km all the way to England to conclude his journey.

Karl Bushby (British) of Goliath Expedition started his journey on foot on November 1st, 1998 in the Chilean town of Punta Arenas. Karl walked northwards through South America, Central and North America, before crossing from Alaska into Siberia, using the semi-frozen Arctic waters of the Bering Strait. With this achievement, Karl and his partner Dimitri Kieffer became the first modern men to walk across the Bering Straits.

Karl's journey will continue westwards through Siberia, down to Russia’s southern border, across Asia and Europe. The finish will be (pending authorization) through the Channel Tunnel and into the United Kingdom. Karl's walk will be a "walk around-the-world" because his route crossed the Equator and Karl will have covered a distance of 36,000 miles in excess of the length of the Tropic of Capricorn. Should Karl go through the town of Irkutsk which is the antipode to his starting point Punta Arenas, then Karl will have achieved a "circumnavigation by walking."

Currently there is only one person in contention for the first human powered circumnavigation, having met all requirements: Jason Lewis (British) of Expedition 360. Jason has crossed the Equator twice, and has already reached the Australian antipode to his route across the Atlantic. Jason is now on the return trip to his home in England on this "circumnavigation by human power," and he is demonstrating to the rest of us that a TRUE Human Powered Circumnavigation is possible.

Precedent - Surface Travel (the hard way): Sir Ranulph Fiennes and his team successfully completed Transglobe in 1982 after over two years of work. Transglobe was the first polar circumnavigation by surface travel, touching the two poles of the earth, which are true antipodes by definition. The story of this journey is told in the book: "To the Ends of the Earth." This expedition did not even have to cross all meridians...

Precedent - Surface Travel (sailing): Sailors typically navigate the interconnected bodies of open water around the world. Many prominent sailing races, including the Vendée Globe, leave from Europe, travel into the South Atlantic, then follow an easterly heading around Antarctica, clearing Cape of Good Hope (tip of South Africa), then Cape Horn (tip of South America) respectively, eventually returning back north to Europe.

The World Speed Sailing Record Council requires that an "Around the World" sailing record claim must have crossed the Equator. Rule 26(a) in "the courses offshore" section of the WSSRC Rules Book is quoted below:

"Around the World, eastbound and westbound"
"To sail around the World, a vessel must start from and return to the same point, must cross all meridians of longitude and must cross the Equator. It may cross some but not all meridians more than once (i.e. two roundings of Antarctica do not count). The shortest orthodromic track of the vessel must be at least 21,600 nautical miles in length calculated based on a 'perfect sphere'. In calculating this distance, it is to be assumed that the vessel will sail around Antarctica in latitude 63 degrees south. A vessel starting in the Southern Hemisphere has to round an island or other fixed point in the Northern Hemisphere but only once that will satisfy the minimum distance requirement."

Precedent - Exclusively For Flights (ballooning): Due to meteorological laws, hot air or helium balloons are dependent on the prevailing winds in the atmosphere to travel around the world. The eastbound jetstream in the southern hemisphere is an example of such winds. Steve Fossett in his historic first around-the-world balloon flight in the summer of 2002, launched "Bud Light Spirit of Freedom" from Australia, drifting east over the Pacific, South America, South Atlantic and the Indian Ocean. His flight took him back across the same longitude he had started over Australia to be complete.

The Fédération Aéronautique Internationale (FAI) has defined the around-the-world flight rules specifically for "Class A: Free Balloons" and "Class B: Airships," the latter of which includes blimps. When such a flight crosses all longitudes, covers a distance which is at least half that of the circumference of the equator, eventually crossing the same longitude where it started, then it is considered an around the world flight. Needless to say, these rules are exclusively for aerial journeys.

FAI never uses the unique expression circumnavigation in its "around-the-world-flight" definition, and never pretends to offer this ruling for any other application (as in surface journeys). FAI has stated in writing that they will not take a position on records by surface travel. FAI does not enforce an antipodal requirement by this around-the-world flight definition, nor does it expect pilots to cross the equator, recognizing the meteorological laws.