ASK!: Life in a trapezoid

By Mike Rudeen, Rocky Mountain News (Contact)

Sunday, May 18, 2008

Athena was studying a map of Colorado and noticed that the state seemed slightly narrower at the northern border than at the southern border - a trapezoid, in a word. She wondered whether that's true and why.

Ryan used National Geographic mapping software, and a gaggle of civil engineering students at the Colorado School of Mines employed spherical trigonometry, to determine that the discrepancy is roughly 21.5 miles.

Will wrote that the eastern and western borders follow meridians of longitude (those lines that go up and down on a globe or a map), and in the Northern Hemisphere the lines come closer together as they go north due to the curvature of the Earth.

All true, says Steve Reiter, a geographer with the U.S. Geological Survey. When Colorado became a state, its eastern and western borders were established at 109 degrees longitude on the west and 102 degrees longitude on the east. But because of the curvature, the seven-degree difference is narrower nearer the North Pole: 21.20682 miles narrower in this case.

Technology being what it was in the mid-1800s, the surveys setting those boundaries weren't precise. But they were accepted, Reiter said, leaving the eastern and western borders several miles west of the designated meridians.

Ready for a new challenge?

Is postdating a check binding? In other words, if I give someone a check dated a week later, can it be cashed or deposited before that date? - Doug

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