Recently, several high and ultra-high degree global harmonic models have been developed. They are typically used in local gravity field modeling via the remove-restore technique, in order to establish accurate and precise local geoid solutions. In the current study, a comparison is performed, concerning Egypt, among the behaviors of the new harmonic models EGM96, GFZ97 and GPM98C with respect to the available local data. These comparisons ascertain that none of these new models recover the long-medium spectral information in a reliable manner, due to the absence of the Egyptian local data during the global solutions for those harmonic models. Among the three investigated harmonic models, the EGM96 model, as a reference field, seems to perform slightly better than the other two models, based on the available Egyptian data set. So, it is recommended to improve the EGM96 model, using the local Egyptian data. |
