Comparison between EGM96 and FCUL96B tailored geopotential model for the north-east Atlantic

A new geopotential model tailored to gravity data in the north-east Atlantic
was developed. The new geopotentia1 model (FCUL96B), completed to degree and
order 360, has been calculated using a new set of 30’ x 30’ mean free-air gravity
anoma1ies obtained from severa1 ocean gravimetric missions which took place from
1975 to 1990. The calculation of the tailored model was based on the OSU91A
coefficient set that was used as a start model. The comparison of EGM96, OSU91A
and FCUL96B, with a1timetric data obtained from ERS1 and TOPEX, reveals a
slightly better accuracy for the FCUL96B model. In this area, the EGM96 geopotential
model reveals a better fit to the gravity field than the OSU91A one but not as good as
the tailored model FCUL96B. From the results we obtained, we verify that a tailored
model can provide an improved reference surface for loca1 and regional solutions, if
the gravity data used in the tailoring process is improved in qua1ity or in density.