Cylindrical projection

Cylindrical projection.

It is a cylindrical and conformal projection, since it preserves the angles and shapes. Distances and surfaces deform a lot.

A cylindrical projection is a map projection using a tangent cylinder. Cylindrical projections are obtained by projecting the spherical surface onto a cylinder secant or tangent to the sphere.

In the cylindrical projection, the resulting map presents a network of parallels and perpendicular meridians. The deformation of the scale is increasing away from the line of tangency, the Equator, where the scale is conserved. Despite this deformation, the fact that the perpendicularity between meridians and parallels is maintained leads to a simple and useful representation in various situations such as navigation.

The most famous is a modified Robinson projection known as the Mercator projection that revolutionized cartography. In it, a line is not (except when it coincides with a meridian or with the equator) the shortest distance between two points, but it has the great advantage, for the navigator, that the angle with the north is constant. A disadvantage of this projection, and in general of all the cylindrical ones, is the great distortion of the scale in zones of high latitude (from 60 to 90 degrees, both north and south of the Equator).

World spherical chart

Until the beginning of the 18th century, spherical chart used to be called a modified cylindrical projection in which the constant heading track, called a rhumb line, was represented, at least approximately, by a straight line. The definitive solution of the problem was only achieved with the construction (because it is not strictly a projection) that is generally called Mercator , because it is the Flemish Gerardus Mercator who is credited with his invention. However, this invention is due to Spaniards (Martín Cortés de Albacar and his disciple Alonso de Santa Cruz, senior cosmographer of Emperor Carlos V).