¿Cuántas variables temáticas se pueden representar en un mapa?
Esta pregunta seguro que os ha rondado por la cabeza y a más de uno le habrá supuesto un problema lograr incluir de forma clara más de tres variables temáticas con sus respectivas leyendas.
El desarrollo de técnicas de La visualización de la información geográfica es una área emergente que cobra protagonisno en nuestra cultura minimalista de la imagen, donde buscamos no sólo transmitir con eficacia información en la menor cantidad de tiempo posible, sino también captar la atención del lector de mapas. Explorar este mundo de la infografia y los mapas es una tarea pendiente para este año nuevo.
A modo de ejemplo una delicia cartográfica, vía strangemaps el mapa del ingeniero Minard sobre la la campaña rusa de Napoleón de 1812. Este mapa ha sido recogido por the economist en un interesante artículo Worth a thousand words.
Citamos literalmente
» It was drawn half a century afterwards by Charles Joseph Minard, a French civil engineer who worked on dams, canals and bridges. He was 80 years old and long retired when, in 1861, he called on the innovative techniques he had invented for the purpose of displaying flows of people, in order to tell the tragic tale in a single image. Edward Tufte, whose book, “The Visual Display of Quantitative Information” is a bible to statisticians, calls it “the best statistical graphic ever drawn”.

Minard’s chart shows six types of information: geography, time, temperature, the course and direction of the army’s movement, and the number of troops remaining. The widths of the gold (outward) and black (returning) paths represent the size of the force, one millimetre to 10,000 men. Geographical features and major battles are marked and named, and plummeting temperatures on the return journey are shown along the bottom.
The chart tells the dreadful story with painful clarity: in 1812, the Grand Army set out from Poland with a force of 422,000; only 100,000 reached Moscow; and only 10,000 returned. The detail and understatement with which such horrifying loss is represented combine to bring a lump to the throat. As men tried, and mostly failed, to cross the Bérézina river under heavy attack, the width of the black line halves: another 20,000 or so gone. The French now use the expression “C’est la Bérézina” to describe a total disaster.

In 1871, the year after Minard died, his obituarist cited particularly his graphical innovations: “For the dry and complicated columns of statistical data, of which the analysis and the discussion always require a great sustained mental effort, he had substituted images mathematically proportioned, that the first glance takes in and knows without fatigue, and which manifest immediately the natural consequences or the comparisons unforeseen.” The chart shown here is singled out for special mention: it “inspires bitter reflections on the cost to humanity of the madnesses of conquerors and the merciless thirst of military glory”.