Homebrew Map Projections

George Shoemaker, Novemeber 2024

Taking 3D latitude & longitude coordinates and plotting them on a 2D screen.

Equirectangular Projection

As simple as it gets! Use longitude for X and latitude for Y and you get a decent projection.

Equirectangular seriously stretches features horizontally as you approach the poles.

Mercator Projection

A bit more sophisticated. Keep using longitude for X.

Y = map width * ln [ tan( π / 4 + latitude / 2 ) ]

Mercator is know for stretching features vertically as you approach the poles. In fact, the poles themselves result in infinitely large Y values.

Resources used

• Map projection: An intro for multivariable calculus by Professor Mark McClure
• Mercator pseudo code by Michel Feldheim on Stack Overflow
• p5.js to plot polygons on the screen
• Google Earth desktop to trace lat / long polygons
• Hosted via GitHub Pages. View my source repository homebrew-map-projections