Method of Solution

• Solve for a 70x70 satellite only solution (EGM96S).
• Add in direct altimetry and surface gravity normals to derive the 70x70 combination.
• The high degree quadrature solution is developed using EGM96S as a foundation, + the surface gravity data, and the altimeter derived anomalies.
• The block diagonal solution is also built on EGM96S, the surface gravity data and the altimeter derived anomalies, AND uses the quadrature solution as a reference.
• Create a combination 70x70 solution that includes the satellite tracking data from EGM96S, the direct satellite altimetry ( TOPEX, ERS-1 , GEOSAT), and the surface gravity normal equations to 70x70.
• The final product, EGM96, is a blended solution. It consists of:
  • A combination solution to degree and order 70.
  • A block diagonal solution from degree 71 to 359.
  • The quadrature solution at degree 360.
• The error covariance of EGM96 is complete to 70x70. The coefficient sigmas are complete from l=71 to l=360.
• Note that in EGM96, the reference radius is 6378136.3 meters, and the gravitational constant of the Earth was held fixed at the reference value of 3.986004415e+14 m**3/s**2.

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