The precision, reliability and fast availability of GPS-data demanded from applications for early warning tasks result in high requirements with respect to the GPS-instrumentation (GPS-stations). GFZ operates a globally distributed network of GFZ-developed GPS-stations for geodetic tasks since many years, which also fulfill the requirements for early warning tasks.
In the framework of the project GITEWS, GFZ installed GPS reference stations in Indonesia, which should be easily serviceable on-site (figure, center). Based on the long term experience with the GFZ-stations in the global network a new station design was developed where components are installed in modules. The modules and connecting cables can easily be checked and replaced at the front-side of the rack. A necessary integration of components from other manufacturers or of different type (e.g., replacements for out of stock components) after some years of operation is well supported by the modular design. The GPS-antennas of the stations are installed on solid concrete fundaments and low heights above the ground (figure, right). This ensures a high stability even in case of earthquakes and a good coupling of the construction to the ground. The stations have two different and thus completely independent satellite communication systems. The GPS-data measured at these stations is transferred to the warning center in Jakarta in real-time. Due to the specifications this station type is called GPS RTR station (Real-Time Reference). The network of GPS real-time reference stations in Indonesia is the backbone of the GPS-based system-components being established in the national early warning system.