Map Projection Explorer

Every flat map of the round Earth has to distort something: area, angle, distance, or shape. No projection preserves all of them. This explorer projects the globe through twelve classic map projections and overlays Tissot's indicatrix, the small ellipse that turns the invisible local distortion into something you can see. Drag the canvas to recentre the globe and watch the distortion pattern move with it.

Figure 1. The graticule, the Blue Marble Earth texture, and Tissot indicatrices of the selected projection. A circular indicatrix marks a conformal point, an equal-area indicatrix marks an equal-area point, and the diagnostic panel tracks both along the central meridian. Method: forward projection of geographic coordinates, with the indicatrix from the numerical Jacobian in an orthonormal sphere basis.

WHAT TO TRY

Switch to Mercator and watch the Tissot ellipses inflate toward the poles: the indicatrices stay circular (Mercator is conformal) but their area runs away, which is why Greenland looks the size of Africa.

Switch to Mollweide or Hammer: every indicatrix now has the same area (equal-area) but they squash into ellipses, so shapes are sacrificed instead.

Compare Winkel tripel and Robinson, the compromise projections: neither distortion is zero anywhere, but neither runs away either.

Drag the globe so the orthographic, stereographic, or gnomonic projection recentres on a different hemisphere.

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