During the first years of the project most of the wide-ranging work undertaken by the EGSIEM consortium was concerned with the improvement of existing gravity products, to this end there was significant work undertaken on creating a combined solution from the various GRACE Analysis Centres which are represented within EGSIEM. Based on the EGSIEM processing standards, the scientific service delivers the best combined Earth’s gravity field solutions and user-friendly L3 products covering a demonstration period of two years of GRACE data from 2006 to 2007, these have been made available via the project website. For the calculation of the combined solutions, a common denominator needed to be defined to allow for a controlled exchange and combination of the Analysis Centres (AC) solutions. For the first time in the gravity field community, the already existing Solution INdependent EXchange (SINEX) format has been used to exchange the normal equations of the various ACs in the EGSIEM consortium. Single AC solutions as well as the combined solution have been provided to the ICGEM (the International Center for Global Gravity Field Models) where they are archived and are in the process of being assigned with a digital object identifier. The Scientific Combination Service shall be continued as part of IAG’s International Gravity Field Service (IGFS). It is intended that the International COmbination Service for Time-variable Gravity fields (COST-G) will be formally established as a service center under the umbrella of the IGFS. In terms of non expert access to GRACE data the consortium is pleased to report development undertaken on the EGSIEM Plotter which allows for a number of different visualisations of gravity Data and which has been updated continuously since the start of the project, users can now save and share their work created within the plotter, a unique feature developed to encourage cross-disciplinary research at all levels.
Hydrological applications using GRACE data proved that it is possible to derive gravitational based wetness indicators that allow users to quantify catchment anomalies. However, reducing the latency from 60 to less than five days and increasing the temporal resolution to daily for a low degree Earth’s gravity field solution has been a prerequisite to establish a prototype monitoring service. The EGSIEM consortium realized this within the near-real time (NRT) objective. In terms of operational processing, the Analysis Centers at GFZ and TUG are now able to deliver daily global and regional gravity field solutions within less than the projected five days latency in a fully automated manner including computation, internal evaluation and distribution. For the operational test period the consortium successfully ran the service in real-time. In the run up to the NRT service operational test run, the whole GRACE time series from 2002 until 2017 was successfully processed. The resulting post-processing solutions of both GFZ and TUG are publicly available as gridded water storage products at the respective ftp servers, the service is currently on-hold due to the decommissioning of GRACE. The gravitational wetness index derived by the EGSIEM consortium enables users to monitor (sub-) surface hydrological mass variations in near-real time. The primary effort of this service was therefore the reliable and robust derivation of the wetness index from the products provided by the NRT.
