The objective of this TFG is the implementation of an extraction tool of ionospheric data through messages of EGNOS (European Geostationary Navigation Overlay Service), which allows to monitor the system behavior in problematic days, such as solar storms or geomagnetic disturbances and to analyze the current historical Available FTP service in the European Space Agency (ESA). EMS2IEWAS generate ionospheric data with a resolution (15 min) better that provided by the ESA intervals of 2 hour, enabling to IOnospheric determination and Navigation based on Satellite And Terrestrial systems (ION SAT) make more accurate comparisons within their investigations. During the performance of this TFG was necessary to understand the global positioning system GPS, limits, problems or deficiencies thereof and current solutions. In this work is documented and explains the operation of both GPS and EGNOS systems with emphasis on their ionospheric models. Operation and existing types of messages Satellite Augmentative Based Systems (SBAS), programmed into the software, for obtaining ionospheric data. The software has been developed in Java, object-oriented, significantly improving the flexibility and understanding compare with other existing decoders programming softwares. This tool developed is compatible with various operating systems and is the first free tool with the ability to decode multiple messages of EGNOS. The software has been developed within the project Monitor2 from ESA, in conjunction with the software IEWAS made by IONSAT research group. The TFG has contributed a detailed analysis of the data provided by the software during the geomagnetic storm of St. Patrick (March 2015) and the detection of two strips of errors with a 36-hour shift in the data stored in the server Message EGNOS Server (EMS) of the ESA. This important fact has been notified through a comprehensive report to the ESA to promote its corrections.