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Hello Robert,

I understand that you are asking about linear distances. Defining the
Tropics and the Arctic Circles as parallel circles at geodetic latitudes
eps and 90-eps, respectively,

where eps = 23.44 deg (J2000.0), and a = 6378.14, f = 1/ 298.257 (WGS 84),

an approximative formula (+/- 50m) given by Andoyer (see e.g. Meeus,
Astr. Alg. p.85) obtains

     D(Equator - Tropic)   =   2593.25 km
     D(Pole - Arctic)         =   2616.66 km


For what it is worth, the geocentric latitudes of both these parallel
circles are 8.4' lower than the corresponding geodetic ones (give or
take 1"). This follows from

     phi - phi' = 692.73" sin (2 phi) - 1.16" sin (4 phi)
(see Meeus, Astr. Alg. p.83).

discarding the 2nd term.

I can run the computation for different parameters, if you wish.

Best regards

Herbert Prinz




Gent van R.H. wrote:

>Hi,
>
>On a truely spherical earth the distance between the North Pole and the
>Arctic Circle is equal to that between the Tropic of Cancer and the equator.
>
>In reality both distances should be slightly different due to the flattening
>of the Earth.
>
>Does anyone know the exact numbers, based on current estimates for the
>earth's diameter and flattening?
>
>Thanks in advance,
>

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