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    Re: Impressed with the Raft Book
    From: Frank Reed
    Date: 2010 Jan 31, 18:46 -0800

    Mike Boersma, you wrote:
    "As cloudy and cold as it has been here in Western Michigan, I instead used data from the US Naval Observatory for my local area as the time for the sunrise, sunset, and length of day."

    That's what I had guessed you had done, and this has to work simply by mathematical consistency. We know that the length of the day is sensitive to latitude except right at the equinoxes, so if we calculate the exact length of the day from the latitude (or if we take such calculations from USNO data), then naturally if we use some method to reverse the calculation, we get back the latitude that we put in. But in the real world, the observed times of sunrise and sunset are variable for a number of reasons and those variations will significantly diminish the accuracy of this approach to finding latitude. It's certainly not a worthless method, but its accuracy is low.


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