INTERNATIONAL borders are often tricky to chart on maps. Tangible topographic features can be pinned down by satellite imagery but the boundaries between many states are unmarked and fiercely contested. Perimeters may be formed by rivers or roads but they may also cross mountains, deserts and war zones. Some borderlands have been fought over for hundreds of years and changed hands dozens of times. And some countries, such as India, which is embroiled in a number of territorial disputes, even have strict laws on where their boundaries must be depicted on maps. So how does Google Maps, the most heavily-consulted mapmaker, deal with disputed borders? All maps are political constructions: even the most carefully drawn will betray some geopolitical bias. When traditional print cartographers are faced with questionable borders, they have a number of options, all of which require judgement from the mapmaker. Depending on the purpose and context of the map they may choose to mark a border with a dashed line or special shading to highlight the contention. They may show two borders, each reflecting a national claim with the disputed land in-between. Or they might choose to draw a definitive bold line, disregarding any territorial disputes or deliberately taking one side or the other. The Economist typically publishes several maps a week, often covering areas of disputed territory. In a map of Europe published on August 30th we depict Crimea with stripes of two colours, for example, to represent the territorial dispute between Ukraine and Russia. Such decisions are under constant review.

Google Maps has the most comprehensive map set and the largest readership in the world—with a billion users each month. This global audience has prompted Google to produce several local versions of maps for the 200 countries it covers. As well as being written in different languages, the maps also conform to local laws. Mostly Google acts like a traditional cartographer: solid grey lines mark international borders; dotted grey lines show "treaty" and "provisional" boundaries; and a dashed grey line indicates "disputed" borders between countries. But Disputed Territories, a website created by wonks at the Massachusetts Institute of Technology, identifies 12 regions where Google presents different borders to different audiences depending on where they are in the world. Crimea is one such example: when viewed on Google Maps from a browser in Ukraine, no national border is shown, including it within that country’s sovereign territory (see central picture). But when viewed from a computer in Russia the peninsula is demarked with a solid grey line as part of Russia. Viewers elsewhere see a dashed line, recognising the uncertain status of Crimea since Russia annexed it from Ukraine in March. Google also presents six versions of the borders around the Spratly Islands, which are claimed variously by Brunei, China, Taiwan, Malaysia and the Philippines.

When Google launched its mapping service in February 2005 it argued that "maps can be useful and fun". But a decade on, Google’s size and dominance in such a sensitive field mean that its maps are far more than that. Indeed, they have occasionally been drawn into diplomatic squabbles between testy neighbours, a testament to the authority its maps now command. The flexibility of the internet means Google can dodge some of the complaints levelled against the subjectivity of mapmakers. But even with new technology, some of the old constraints of cartography remain.

Dig deeper:

An infographic on disputed borders (Feb 2012)

Crimea in the Russian imagination (March 2014)

How mapmakers are competing for your smartphone (Oct 2012)