The History of Cartography — Reading

Passage

A Every map is a lie, and the useful question is which lie it tells. Representing a curved surface on a flat one is geometrically impossible without distortion, a fact Gauss proved formally in 1827. A projection can preserve shape, or area, or direction, but never all three, so the cartographer must decide what to sacrifice. This is not a limitation to be engineered away; it is a property of the problem. B The Mercator projection of 1569 illustrates the trade-off well, and is routinely criticised for the wrong reason. Mercator's purpose was navigation: on his projection a line of constant compass bearing is a straight line, which is precisely what a sailor needs and no other common projection provides. The cost is that area inflates enormously towards the poles, so that Greenland appears comparable to Africa when it is roughly a fourteenth of its size. The projection is not wrong; it is being used for classroom walls rather than for ships. C Early mapping was frequently more concerned with meaning than measurement. Medieval European mappae mundi placed Jerusalem at the centre and east at the top, arranging the world theologically rather than geographically. The Hereford Mappa Mundi of around 1300 is a religious argument in cartographic form. Judging such maps as failed attempts at accuracy misunderstands what they were attempting. D Systematic surveying changed the discipline. The Cassini family mapped France across four generations from the 1670s using triangulation — measuring one baseline precisely, then deriving all further distances from angles. The resulting maps were accurate enough to reveal that France was smaller than previously believed, prompting Louis XIV's remark that the surveyors had cost him more territory than any war. The Great Trigonometrical Survey of India, begun in 1802, took some seventy years and killed a substantial number of its participants through disease and accident. E Maps have always served power, sometimes overtly. The 1884 Berlin Conference partitioned Africa among European states largely using maps of territory none of the negotiators had visited, and many of the resulting straight-line borders remain. National atlases have routinely depicted disputed territory according to the publisher's government, which is why some map providers now serve different borders to users in different countries — a technical solution to a political problem that quietly abandons the idea of a single correct map. F Digital mapping has changed what a map is more than how it looks. A paper map is fixed and shows everyone the same thing; a digital one is generated per request, and increasingly personalised. The consequence is that two people searching the same area may see different results, and the ranking of what appears is commercially determined. Meanwhile the shared, checkable object has largely disappeared: a printed map could be examined and disputed, whereas a rendered view cannot readily be compared with anyone else's. G What has not changed is the necessity of selection. A map showing everything would be the size of the territory, as Borges observed in a story about an empire whose cartographers produced exactly that and whose citizens sensibly abandoned it. Usefulness requires omission, omission requires judgement, and judgement reflects the interests of whoever is making it. The honest position is not that maps should be neutral, which is unachievable, but that their choices should be legible to the people using them. H Digital mapping has not resolved the old debates about projection and selection; it has largely automated and hidden them from the ordinary user. A widely used online mapping service defaults, for most of its users, to a variant of the Mercator projection at the street-navigation scale that Gerardus Mercator himself would recognise, for the pragmatic reason that Mercator preserves the local angles and shapes needed for turn-by-turn direction, whatever its well-documented distortion of relative size at the global scale. What has genuinely changed is personalisation invisible to the map's own reader: two people searching the same online map for the same city can see different results, different points of interest highlighted, and different routes suggested, based on data the platform holds about them individually, without either user having any way to know what the other was shown or why. Cartographers who study the shift describe it as a move from a single, at least publicly inspectable set of editorial choices — the paper map's typeface, colour and selection, all fixed and visible on the page — to millions of individually tailored, algorithmically generated and essentially unauditable ones. The map has not become more neutral in the digital age. It has become considerably harder to interrogate.

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