I have a basic question : Earth has 181 latitude lines, each having distance of 111 km. if i multiply that i will get 20091 KM, which could be the sum of distance from north pole to south pole i.e Diameter of earth, but the original diameter of earth is 12742 km, where does the 8000 Km value goes?

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    $\begingroup$ Ummm, 180 latitude lines and you mean the distance at the equator and that gives you the half-circumference, not the diameter. This question should probably be closed, sorry. $\endgroup$ – user967 Dec 10 '16 at 20:24
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    $\begingroup$ As Barry said, you are calculating the length of the half-circle over the earths' surface, not the diameter through the earth. $\endgroup$ – Jan Doggen Dec 10 '16 at 22:41
  • $\begingroup$ @Barry A minor quibble: 180 gaps between whole degrees of latitude, but only 179 latitude "lines" ( well circles really) -- the poles are points only. $\endgroup$ – Spencer Dec 12 '16 at 20:13

This question is more about surveying than earth science.

OK. Assume the Earth is a perfect sphere. There are 360 degrees in a circle.

One nautical mile is 1 minute of arc. There are 60 minutes in a degree and 21 600 minutes in a circle (60 x 360).

Now, one nautical mile is 1.852 km, therefore, the circumference of the Earth is 40 000 km.

The circumference of a circle is given by ${\pi}d$, where $d$ is the diameter. Divide 40 000 km by $\pi$ & the diameter of the earth is 12 733 km

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  • $\begingroup$ You've given a reasonable approximation to answer the question, but of course, since the Earth has an equitorial bulge, the whole-degree parallels are vatying distances apart. $\endgroup$ – Spencer Dec 13 '16 at 3:45

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