Length of one minute of arc of a meridian.
Length of one minute of arc of meridian: It is known that a meridian has a form very close to an ellipse.
Because of this, in various points of the meridian at different latitudes, the radius of curvature of the elliptical meridian will have different values. Minimum at the Equator and maximum to the poles.
From the same cause, the length of arc of a meridian will be less at the Equator and higher to the poles.
With precision measurements carried out in different places at the same latitude, it was found that the length of 1 minute of arc is absolutely not the same all over. But the differences are so small that can be neglect.
Length of one minute of arc of Equator.
Length of 1 minute of arc of Equator: This value can be considered constant for the entire circumference of the Equator. The differences from one meridian to another are negligible.
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