Projection

What it does

Every flat map distorts the globe. Web Mercator, used by most web maps, keeps angles but inflates area by 1/cos²(latitude). Greenland appears far too large. For a road map that can be acceptable. For maps about amounts, such as population, land cover, emissions, or votes, area distortion can mislead.

Changing projection changes the projection the map is computed in, not only how it looks. Choices include Equal Earth, Mollweide, EPSG:6933, polar Lambert azimuthal and stereographic, alongside Mercator. The panel marks which are equal-area.

This is not the same as the 3D tool's globe. The globe changes rendering. This changes the projection.

OpenLayers only. Of the four engines, only OpenLayers can use these view projections.

Using it

Pick a projection. The map is rebuilt in that projection, keeping the ground scale you were at. The view stays where it was even though the zoom number changes, because zoom is relative to a projection's own extent.

Choosing a regional projection from outside its area moves to the middle of that region rather than showing you the blank beyond its edge. For example, the Antarctic projection moves to Antarctica when you are looking at Europe.

In your own map

Add projection to a toolbar, on an OpenLayers map. A starting projection can also be set in map.projection, which is applied when the view is built rather than afterwards. A map configured for Equal Earth never draws a Mercator frame first.

Extending it

A projection must declare the latitudes it can be measured over. Polar stereographic sends its antipode to infinity, so world sampling can produce an unusable extent. Every cataloged projection must also be metre-based.

Vector tiles survive the switch because OpenLayers reprojects them in the canvas renderer.