Curvature math questions based on latitude

OK. Don’t go psycho on me if I’m wrong here. I’m just asking questions. It seems to me that the curvature math would have to be different if you are looking east-west on the various lines of latitude because the circumference would be more shallow than if you were at the equator or looking at any other direction apart from due east-west. For example, on my Lake Michigan test, we were on the 41.5 degree latitude. At that latitude, the circumference of the globe is not 24,874 miles. Rather, it is 18,630 miles, which would seem to require a much greater curvature than the usual 8 in. per mile squared. I’m not very mathematical, so if I am wrong, please tell me why – nicely. 🙂

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