To circumnavigate a place, such as an island, a continent, or the Earth is to travel all the way around it by boat or ship. More recently, the term has also been used to cover aerial round-the-world flights.
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.
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.
Transglobe was the first polar circumnavigation by surface travel, touching the two poles of the earth, which are true antipodes by definition.