Document Type : Original Article
Department of Surveying Engineering, Arak University of Technology, Arak, Iran
Department of Surveying Engineering, Zanjan University, Zanjan, Iran
Gravity field models derived from the Gravity Recovery and Climate Experiment (GRACE) satellite mission are affected by the orbital arrangement of the satellites of this mission and the spatial dependence of the gravity field coefficients, which manifest themselves in the form of north to south strips in the maps of corresponding products. One of the common ways to deal with this phenomenon is to use a Gaussian filter to reduce the contribution of higher-order coefficients and to extract realistic images of the surface-mass variability. In this paper, the applicability of the two-dimensional wavelet transforms as a non-statistical method to reduce the effect of vertical components in GRACE products including the mentioned strips, has been tested and the results for different levels of transformation, as well as for using various base functions have been evaluated and this results have been compared with the result of applying Gaussian filter on the data of mass change derived from GRACE in Iran.
The results indicate that although the two-dimensional wavelet transform can inherently be used to reduce the striping error of images, the wavelet-based de-striping of GRACE products is at most as effective as using the Gaussian filter of 100km, while previous studies showed that the application of the Gaussian filter of 350km would be the optimal radius to extract the hydrological signals in Iran. However in the case of wavelet transformation, the most important issue is the number of transformation levels such that applying the wavelet transforms at levels 3 and 4 have led to the closest results to the outputs of Gaussian filtering.