Why a country looks smaller at the globe’s edge

The globe is also an image on a flat screen

RealWorldMap’s globe view uses an orthographic projection. PROJ describes this as a perspective azimuthal projection showing one hemisphere at a time. The visible disk is a way to depict a sphere, not a flat equal-area world map with a circular border.

A globe is useful, but its screen image is not an accurate area ruler. Near the edge you see the surface at a shallow angle; on the far side you do not see it at all. A country’s footprint in the image therefore depends on the viewpoint.

Šaltiniai: PROJ · Orthographic projection

Think of a sticker on a ball

Put an imaginary sticker on the front of a ball, then turn the ball. The sticker seems narrower as it approaches the side, although you have not cut or stretched it. The changing silhouette is foreshortening: a property of the view.

Country outlines behave in the same way. A coastal detail can disappear behind the visible horizon before the rest of the country does. Comparing a centered country with an edge-on country mixes geography with the angle from which you are seeing it.

Area is calculated before it becomes a silhouette

The Equal Earth atlas’s area estimate comes from spherical boundary geometry, not the number of visible pixels. Rotating the camera can change the silhouette without changing that geometric area, even when part of a selected country is hidden.

The globe is a good tool for orientation and for seeing the continuity of a curved world. For an area-ratio overview, Equal Earth supplies a more appropriate flat display. Do not infer a territory’s size from how much of its front-facing silhouette happens to remain visible.

Šaltiniai: D3 · Spherical area and distance

Move one country from center to rim

Search for a country to bring it toward the center, then rotate the globe slowly. Its outline narrows as it approaches the rim, and part of it disappears behind the visible hemisphere. Keep the zoom fixed: the change comes from the viewing angle, not a change in the country’s land.

Bring the country back toward the center and the hidden part returns. A Pacific Ocean divided between the ends of a flat world map also becomes a continuous surface on the globe. Rotation reveals both the country’s outline and the connections concealed by a flat map’s seam.

Šaltiniai: PROJ · Orthographic projection

Common questions