4 ms·

Wouldn't this be to ensure that one degree of latitude is always approximately the same distance? (i.e. one mile)

• michaelochurch 15y ago
  No. It has to do with how coordinates were calculated before we had good data on the Earth's oblation. Latitude was calculated based on the solar elevation (measured by sextant) at noon. For example, at 40 degrees north (by definition) the sun will be at 50 degrees at noon on an equinox. Longitude is a different story; it's relatively recent that we've been able to calculate that. Sailors in the 17th century had sextants and solar tables and could figure out their latitude easily, but had no idea where they were in terms of longitude.
  • dredmorbius 15y ago
    Replying off the top of my head, but IIRC once astronomical phenomena became known and observable, these could provide constant "clocks" which could be verified at different points on the Earth's surface. In particular, transits/occlusions of planets, moons, or stars could be viewed from different points. While observations regarding the Earth's moon are subject to some parallax, by the time you're looking at other planets (or their lunar systems), the error is minimal. We're talking Keplerian / Gallilean times onward (telescopic observation and orbital mechanics) for the most part, though some observations may have been possible / performed in earlier times. Turns out that Gallileo and Halley proposed such methods in 1612 and ~1683. Accurate navigational chronometers came along in the late 18th century.
• cromulent 15y ago
  No - one degree of latitude still varies. One minute of latitude is a "sea mile", which varies. A nautical mile is 1852 meters which is the closest round number to the mean sea mile.