Wavelet Analysis and Reconstruction of GOCE/GRACE Geopotential Models Using GPS/leveling Data in Turkey
19/09/2016 | 17:30 | Session 2: Global gravity field modelling
Author(s): Serdar Erol, Bihter Erol and Mustafa Serkan Işık
Serdar Erol, Bihter Erol and Mustafa Serkan Işık
The sequential launch of the Earth gravity field missions since the beginning of the century leads unprecedented improvement in geopotential models, the GRACE mission contributes the determination of the temporal variations in Earth gravity fields where as the GOCE mission data improves the global gravity field models in terms of accuracy and spatial resolution significantly. Regional validations of the products by the satellite missions are essential to clarify the amount of the improvement. However verifying the contribution of the satellite mission in varying bands of spectrum, spectral assessments of the models are applied. Hence the signal power depending on the increasing commission error at the higher degrees of spherical harmonic expansion can be judged clearly and an optimal degree for the model, which provides the calculation of accurate parameters through the model, can be decided. In this study an assessment of the recent releases of GOCE/GRACE based and GOCE-only geopotential models (DIR-R5, TIM-R5, respectively), depending on the terrestrial data in Turkey, is provided. In the assessment of the models, ultra-high resolution EGM-2008 is employed as reference model for the enhancement of the DIR-R5 and TIM-R5 models spherical harmonic expansion. Beside the performance assessment of the models in order to decide the spectral band that it contributes the best, a strategy to improve the spectral quality of tested models with decomposition and after that re-construction of the spectral bands that are flagged as highly contaminated by noise, is applied. The decomposition/reconstruction procedure rely on achieving an optimal amount of improvement via conserving the useful component of the geopotential model as much as possible and completing the filtered geopotential model with EGM-2008 model in the appropriate spectral bands. Hence a new spherical harmonic expansion model with the advantage of GOCE/GRACE contribution in specific bands of the spectrum is provided. In the meanwhile the performance of Wavelet decomposition methods in improvement of geopotential models is tested as well. The fund for this research is provided by the Scientific and Technological Research Council of Turkey (TÜBİTAK) under contract number 114Y581.