It is well known that using a global geopotential model, as a reference field, is crucial for a high quality local (or regional) gravimetric geoid determination. However, the application of this technique would only be reliable, if the region under investigation has gravity data contribution to the used harmonic model. EGM96 represents the most recent high degree global geopotential model that is completely released to the geodetic community. However, during the solution for that model, no Egyptian terrestrial gravity data were taken into account. This paper presents an attempt to locally refine the EGM96 harmonic model to fit Egypt better. Using least-squares collocation technique, corrections for the EGM96 spherical harmonic coefficients along with their error estimates are predicted based on the recent available gravity data in Egypt. Using the refined EGM96 model, which will be denoted as EGM96EGR, as a reference field showed an improvement in gravity anomaly smoothing by about 40%, which represents a great efficiency in low frequency gravity field modeling. |
