It's a small world (enlarge)



Very little of the world's land can now be thought of as inaccessible, according to a new map of connectedness.



The maps are based on a model which calculated how long it would take to travel to the nearest city of 50,000 or more people by land or water.



The model combines information on terrain and access to road, rail and river networks. It also considers how factors like altitude, steepness of terrain and hold-ups like border crossings slow travel.



Plotted onto a map, the results throw up surprises. First, less than 10% of the world's land is more than 48 hours of ground-based travel from the nearest city.



What's more, many areas considered remote and inaccessible are not as far from civilisation as you might think. In the Amazon, for example, extensive river networks and an increasing number of roads mean that only 20% of the land is more than two days from a city - around the same proportion as Canada's Quebec province.



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Nowhere, three weeks from anywhere



It's official, the world's most remote place is on the Tibetan plateau (34.7°N, 85.7°E).



From here, says Andy Nelson, a former researcher at the European Commission, it is a three-week trip to the cities of Lhasa or Korla - one day by car and the remaining 20 on foot.



Rough terrain and an altitude of 5200 metres also lend it a perfect air of "Do Not Disturb".

A road to somewhere (enlarge)



Based on satellite data from the US Geological Survey's National Imagery and Mapping Agency, this map shows how the world is riddled with roads.



These can be further broken down to show road types (see next image), which dictate how quickly a driver can zip along them (see table). Advertisement

Detail of roads in west Africa



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Keeping track of trains (enlarge)



Unlike roads, which can evolve out of any old dirt track, railways require skilled labour and considerable investment. As a result, they are confined mainly to the richer nations of Europe, the US, Australia and Japan.



Railway networks in India, Argentina and parts of Africa give clues to their colonial heritage.

The shipping news (enlarge)



With the brightest colours representing the busiest shipping lanes, the English Channel, Mediterranean and South China Sea stand out as major trade routes.



Regions to the far north and south are left out in the cold, at least for now.

The shipping news - detail



China's flourishing export trade is clearly seen, with some of the world's busiest shipping lanes.

Water world (enlarge)



The planet's navigable rivers provide not only food and water, but also a valuable way of getting from A to B.



In areas where no roads penetrate, such as the Guiania region of eastern Colombia, river travel is simply the quickest way to get around.



The mapping model assumes a river travel time of 3 minutes per kilometre, though its creators point out that this will vary with flow, season and political stability.

Patchwork planet (enlarge)



This map shows the different types of landcover on the Earth's continents.



Click to see a larger version, including a key