Saturday, March 01, 2014

Vector Earth

I added a new HTML5 experiment to my website: Vector Earth. Inspired by the xkcd now comic, I downloaded some vector map data and tried experimenting with making some of my own map projections. The first projection I implemented was the Azimuthal equidistant projection, similar to what was used for the xkcd comic. If you are interested in map projections, Jason Davies has implemented some very cool demos.

While I was implementing the map projection, I encountered a bug where there was an unnatural vertical line cutting through Siberia. I went to Google Maps to see what Siberia was supposed to look like, and was amused to find that Google Maps seemed to have the same bug!

In both the vector and satellite data, there are strange discontinuities along this line. It turns out that this line is the threshold where 180 degrees longitude meets -180 degrees.

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