Projection Type
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Preserves
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Max Areal Distortion
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Angular Distortion
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Every map is a lie. The Mercator projection that most of us grew up with makes Greenland look as big as Africa (it's 14 times smaller). Cartographers have been debating the “best” world map for over a century, but most people have never seen the evidence. This project was inspired by the cartographic controversy surrounding the Mercator projection and the work of Nicolas Auguste Tissot, who in 1859 proved a mathematical way to visualize exactly where and how every map distorts reality.
Projection Lab is an interactive map projection distortion explorer. It implements 10 different map projections and overlays Tissot's indicatrices — a grid of ellipses that reveal exactly how each projection distorts area, shape, and angles. You can compare any two projections side by side, toggle the graticule grid and landmass outlines, and read quantitative distortion measurements for each projection.
Each map projection is implemented as a forward transformation function that converts longitude/latitude coordinates to planar (x, y) coordinates using the specific mathematical formula for that projection. Tissot's indicatrices are computed using numerical differentiation: for each grid point, the Jacobian matrix of the projection is approximated via finite differences, then the eigenvalues of the metric matrix in the orthonormal east/north frame (equivalent to an SVD) yield the exact principal scale factors, orientation, and area scale of the distortion ellipse. The simplified continent outlines are stored as arrays of (lon, lat) coordinate pairs and projected through each transformation.