The precision, reliability and fast availability of GPS data required by applications for early warning tasks result in high standards with respect to the GPS instrumentation (GPS stations). GFZ has been operating a globally distributed network of GFZ-developed GPS stations for geodetic tasks for many years, which also fulfil the requirements for early warning tasks.
Within the framework of the GITEWS project, GFZ installed GPS reference stations in Indonesia, which needed to be easily serviceable on-site (Figure 1, centre). 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 types (e.g., replacements for defective, obsolete components) after several years of operation is well supported by the modular design. The GPS antennas of the stations are installed on solid concrete foundations at low heights above the ground (Figure 1, right). This ensures high stability even, in the event of earthquakes and firm coupling of the structure 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 centre in Jakarta in real-time. Due to the specifications, this station type is called GPS RTR (Real-Time-Reference) station. 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.