Featured Maps: I Didn't Expect That! (6 March 2010)

A friend recently expressed surprise that ANC-DFW is less than 200 miles (only 317 kilometers) farther than ANC-ORD. Plotting the great circle routes helps visualize why:


Using an orthographic projection is even better for problems like this. The orthographic projection, which depicts one hemisphere as seen from space (mathematically, the perspective is from infinitely far away), has the property that any great circle passing through the center of the map is a straight line. Here's how ANC-ORD vs ANC-DFW looks on this type of map:

orthographic projection of ANC-ORD/DFW

My family holiday trip provides another example of a case where the relative distances aren't what you'd expect. We went to London for Christmas, flying SFO-LHR on Christmas Eve and returning LHR-LAX-SFO on New Years Day. It seems like LHR-LAX should be shorter than LHR-SFO but it isn't:

orthographic projection of LHR-SFO/LAX

Many people enjoy using the Great Circle Mapper to help understand geographical puzzles like this. Happy exploring!


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