GPS-controlled tide gauges in Indonesia – a German contribution to Indonesia's Tsunami Early Warning System

Abstract. Coastal tide gauges do not only play a central role in the study of climate-related sea level changes but also in tsunami warning systems. Over the past five years, ten GPS-controlled tide gauge systems have been installed by the German Research Centre for Geosciences (GFZ) in Indonesia to assist the development of the Indonesian Tsunami Early Warning System (InaTEWS). These stations are mainly installed at the Indonesian coastline facing the Indian Ocean. The tide gauge systems deliver information about the instantaneous sea level, vertical control information through GPS, and meteorological observations. A tidal analysis at the station's computer allows the detection of rapid changes in the local sea level ("sea level events"/SLE), thus indicating, for example, the arrival time of tsunamis. The technical implementation, communication issues, the operation and the sea level event detection algorithm, and some results from recent earthquakes and tsunamis are described in this paper.