ALEGRO: a step towards a maritime GALILEO GBAS

Kurzfassung

In the framework of the establishment of the Rostock Research Harbour, the project ALEGRO, aiming at the “Installation of a local maritime augmentation system to support high precision application and service of GALILEO within the Rostock Research Harbour” was initiated by DLR under the support of the Government of German Federal State Mecklenburg-Vorpommern. According to the baseline of the project, aiming at the Deployment of a maritime Test Bed for the Application and Validation of Galileo Core Technologies in the maritime Environment, it was decided to perform the projects in three stages. Within the first step the flexible EVnet (Experimentation and Verification Network of the IKN) based infrastructure was developed as a basis for the GNSS algorithms to be developed and implemented in the second step. Finally, in the last step experimentations will be performed to verify and demonstrate the application potential of the maritime GBAS system, namely to Galileo. In the paper the outcomes of the first step will be presented and discussed. To this purpose, the ALEGRO infrastructure components will be introduced and the methodologies for the investigation of the performance and the quality of real time positioning will be detailed. The basic intention was to identify and evaluate signal disturbances in the harbour surrounding and to validate algorithms that have been developed by the authors for the detection of environmental and propagation effects decreasing the signal quality and availability. Therefore an EVnet compatible reference station was operated to provide the opportunity to detect various signal disturbances such as multipath and shadowing effects, aiming to place the reference station at an optimal position. For the first experiments and evaluations, a reference station tracking current GPS and GLONASS systems was equipped with a RTK option. At rover site, three different positioning methods (GPS GLONASS stand-alone, GPS/EGNOS, and real time RTK using GPS and GLONASS) have been implemented. Since all receivers make use of the same antenna, equal receiving conditions could be assumed, and therefore the derived quality and reliability parameters are comparable. Professional geodetic GPS processing software was used to compute high precision reference trajectories for the evaluation of the accuracy of the various rover positioning results. The experiments have been realized on four consecutive days in almost the same scenario. As a result of the data analysis we have gained first experience and knowledge concerning infrastructure and algorithms needed to achieve reliable real-time positioning performance in the maritime environment. On water, in the air and ashore the future European Satellite Navigation System GALILEO will offer an alltime high precision and integrity. Because of its modular set up and expansibility ALEGRO can beconsidered a basis for the development of future Galileo GBAS systems for safe and efficient maritime transport and traffic processes like collision avoidance, docking manoeuvre and cargo handling.