Re: 2nd SDP4 failures case

jamesv@softcom.net
Thu, 03 Apr 1997 19:07:27 -0800

Bruno Tilgner wrote:

>There are other constants in the code which could potentially be responsible
>for different results. For instance in my code the Earth's flattening and the
>J constants are those of WGS72. I have not yet tried what will happen if I
>replace them with more recent values.

I'm playing with SGP4 and SDP4 right now -- I changed WGS72 to WGS84 and
did not detect any difference in the output.  The changes in the constants
are very small.

WGS84 was adopted as the standard frame for the GPS system.

6378.135         Earth equatorial radius - (WGS '72)
6378.137         Earth equatorial radius - (WGS '84)

1/298.26         Earth flattening (WGS '72)
1/298.257223563  Earth flattening (WGS '84)

398600.8         Earth gravitational constant (WGS '72)
398600.8005      Earth gravitational constant (WGS '84)

1.0826158E-3     J(2) form factor (WGS '72)
1.08263 E-3      J(2) form factor (WGS '84)


_______________________________________________________
Jim Varney        jamesv@softcom.net     Sacramento, CA