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Conformal, equal-area and equidistant projections

Mercator is considered a conformal projection because it preserves local shapes and angles (but distances and areas may be distorted). These projections are commonly used in navigation and weather maps. It's the projection used in Google Maps.

Although azimuthal projections show true distances from a central point, there exist no projections that preserve distances between arbitrary points. Equidistant projections are projections that have equally spaced parallels. There do exist, however, projections that preserve distance between two selected points, as the two-point equidistant projection (see the d3.geoTwoPointEquidistant projection) and others that minimize distortions near three or ...