Geodetic model used by SGP4

From: Thomas Fly (thomasfly@j2ee-consultants.com)
Date: Sun Jan 04 2004 - 01:22:26 EST

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    I wouldn't think that the SGP4 algorithm itself is tied to a particular geodetic
model (though some of the constants used may be affected), but it seems that a
particular TLE (i.e., SGP4 state vector) must implicitly reference a particular
geodetic model. (My SGP4 Java implementation- which traces its roots back to the
apparently original Fortran code- references WGS '72.)

It may be that the difference between WGS '72 and WGS '84 ain't worth spittin'
at (unless you're trying to part somebody's hair with a cruise missile), but
enquiring minds want to know.

          Equatorial Radius | Flattening
        + ----------------- + --------------|
WGS '72 | 6378.135          | 1 : 298.26    |
WGS '84 | 6378.137          | 1 : 298.25722 |

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