Web Mercator

Web Mercator, previously known as "Google Mercator", is the most popular projection for publishing dynamic maps on the Internet. Open up GoogleMaps and zoom out so you can see the distortion in Antarctica. This is the reason that Web Mercator is not used much for global analysis.

Note: When I use "United States" in the video, I really should have said "Continental US".

The Math

One of the reasons that web Mercator is so popular is that the mathematics behind it are so simple compared to other projection methods.

• LonInRadians=Longitude * 0.01745329252
• LatInRadians=Latitude * 0.01745329252
• Easting = LonInRadians * 6378137.0  –Multiply by the radius of the earth
• Northing = 3189068.5 * Log((1+Sin(LatRadians))/(1-Sin(LatInRadians)))

This relatively simple math makes it fast to convert between geographic corodiantes and projected coordaintes.

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