Equal Earth projection

The Equal Earth map projection is an equal-area pseudocylindrical projection for world maps, invented by Bojan Šavrič, Bernhard Jenny, and Tom Patterson in 2018. It is inspired by the widely used Robinson projection, but unlike the Robinson projection, retains the relative size of areas. The projection equations are simple to implement and fast to evaluate.

We chose this as the default world map projection for Highcharts because it is visually pleasing like Robinson, but avoids the political problem of rendering high-latitude regions like Europe and North America larger than tropical regions.

Miller projection

The Miller cylindrical projection is a modified Mercator projection, proposed by Osborn Maitland Miller in 1942. Compared to Mercator, the vertical exaggeration of polar areas is smaller, so the relative size of areas is more correct.

Highcharts used this as the default map projection for world maps until the Map Collection v2.0 and Highcharts v10.0, when projection math was moved to the client side and EqualEarth chosen as the default world map projection.

Web Mercator projection

Web Mercator is a variant of the Mercator map projection and is the de facto standard for Web mapping applications.

Web Mercator is primarily created for tiled map services, as when zooming in to smaller scales, the angle between lines on the surface is approximately retained.

The great disadvantage of Web Mercator is that areas inflate with distance from the equator. For example, in the world map, Greenland appears roughly the same size as Africa. In reality Africa is 14 times larger, as is apparent from the Equal Earth or Orthographic projections.

Orthographic projection

The orthographic projection is an azimuthal perspective projection, projecting the Earth's surface from an infinite distance to a plane. It gives the illusion of a three-dimensional globe.

Its disadvantage is that it fails to render the whole world in one view. However, since the distortion is small at the center of the view, it is great at rendering limited areas of the globe, or at showing the positions of areas on the globe.

Lambert Conformal Conic

The Lambert conformal conic projection (LCC) is a conic map projection used for many national and regional mapping systems.

Its advantage lies in mapping smaller areas like countries or continents. Two standard parallels are given, and between these, the distortion is minimal.

In Highcharts, LCC is the default projection when loading a map smaller than 180 degrees width and 90 degrees height.

For custom use, rotation should be set to adjust the reference longitude, in addition to the parallels option.

No projection

This is the raw Equirectangular projection, where the longitudes and latitudes are directly projected onto the plane, except it doesn't run through the Highcharts projection logic.

Notice the lines across the map at high latitudes. This is because the eastern tip of Russia is east of the antimeridian, and thus having longitudes close to -180 and upwards, while connected to the rest of Russia with longitudes from 180 and downwards. In cylindrical and conic projections this is mitigated by doing client-side antimeridial cutting, so that shapes spanning from one side of the plane to the other are cut in two.

Also notice how the lack of a real projection causes the line from LA to Amsterdam render as a straight line instead of the geodesic curve .