# EGMStream Webapp: EGMS Data Downstream Solution
## 1 Introduction  
The European Ground Motion Service (EGMS) is one of the services provided under the Copernicus Land Monitoring Service (CLMS) managed by the Environmental European Agency (EEA) of the European Union (EU) [1]. The EGMS allows the dissemination of Interferometric Synthetic Aperture Radar (InSAR) data, which is now well recognised as fundamental data by European and international scientific communities working on geohazard investigation and management as well as on remote sensing applications [2]. The primary goal of the programme is to support the health of the planet and its environment, benefiting European citizens using data collected by radar satellites for Earth Observation by the European Space Agency (ESA). The development of the EGMS has been preceded by several national Ground Motion Services (GMSs), which laid the groundwork for this pan-European initiative. Among these, Italy played a pioneering role by launching the first GMS in 2007 at a national scale covering the period 1992-2016 [3]: the Italian Special Plan of Remote Sensing of the Environment [4]. This service relies on data from three satellite constellations: (i) ERS1/2 and (ii) Envisat, both operating in C-band (5.6 cm of wavelength) and launched by the ESA, and (iii) the COSMO-SkyMed constellation operating in the X-band (3.1 cm of wavelength)and managed by the Italian Space Agency (ASI). The Italian GMS has been the precursor of further-developed GMSs based on the Sentinel-1 constellation including the regional scale monitoring programme over the Tuscany Region [5], which in 2016 became the first satellite radar continuous monitoring service worldwide. The same initiatives have been developed in the following years by two other Italian regions [6]: Valle d'Aosta and Veneto. In the following years, other European countries followed suit by developing similar services. Norway [7,8] and Germany, for example, launched their GMS at a national scale in 2018 [9]. Additionally, the Agency for Data Supply and Efficiency (SDFE) of Denmark worked on a WebGIS platform to provide InSAR data [10] processed using the SqueeSAR algorithm [11]. Meanwhile, in 2017, the Netherlands began implementing its own national GMS, leveraging the availability of Sentinel-1 satellite imagery. The growing diffusion of GMSs demonstrates that the deployment of the Sentinel-1 constellation has significantly enhanced the possibility for the scientific community and for the end users, such as land managers, to identify and monitor geohazards. This advancement is attributed to the constellation nature of the background mission, its short revisit times, global coverage, and free data access. Extensive studies have highlighted its applications in landslide detection [12, 13, 14, 15], characterisation [16, 17, 18] and monitoring [19, 20, 21], subsidence analysis [22, 23, 24, 25, 26], infrastructure monitoring [27, 28, 29, 30], and the assessment of mining instability [31, 32, 33, 34]. Building on the advancements of national GMSs, the EGMS has been initiated to address the growing demand for free and accessible InSAR data at a continental scale. Since November 2022, the service provides InSAR data covering the Copernicus participating countries, with yearly updates. The first dataset available, spanning 2015-2021, has been subsequently updated year by year with two releases so far: i) 2018-2022 and ii) 2019-2023. The last release comprises approximately 15 billion points, amounting to around 10 TB of downloadable data, exemplifying the scale and richness of the service for monitoring and analysing geohazards throughout Europe. Sentinel-1 data for this service are processed using four algorithms [35]: PSP-IFSAR [36, 37, 38], SqueeSAR [11], GSAR-GTSI [39, 40], and PSI (Persistent Scatterer Interferometry), through an Integrated Wide Area Processor (IWAP) [41, 42]. Nowadays, the two most recent datasets, covering 5 years each, are available, while the first dataset (2015-2022) is no longer accessible.