The sea chart, or nautical chart, is a plane representation of the terrestrial globe constructed on an regular, orthogonal grid of meridians and parallels. In this flat transformation of the spherical surface, areas are subject to a longitudinal distortion that increases as one moves away from the Equator. Distances between places are therefore altered, but meridians and parallels intersect at right angles, as in reality. As a result, any straight line drawn on the map will always intersect the meridians at the same angle. Indeed, the purpose of the sea chart was to allow navigation routes to be drawn along the windrose directions, represented by straight lines. The ship could thus sail toward a point determined by dead reckoning without ever having to change course. That line, however, was not the shortest route between two points, as Pedro Nuñez (1502-1578), cosmographer to the King of Portugal, was the first to recognize in his treatise on the art of navigation of 1537. Nuñez explained that, on the surface of a globe, the line was shaped like a spiral wrapped around the poles. The "rhumb line," now called loxodrome, was not, in fact, a great circle and so did not measure the shortest distance between two points. Moreover, navigating along a great circle was not as easy as navigating along a loxodrome. Although it plots the shortest route, the great circle, called orthodrome, never crosses the meridians at the same angle. To further complicate matters, when transferred to a sea chart, the orthodrome would appear as a curved line that would be hard to represent graphically, forcing the helmsman to change course continuously. The convenience of loxodromes, plotted on the 32 directions of the windrose, promoted the dissemination of sea charts characterized by a dense mesh of radiating lines, with navigation routes running between their nodes.