Natural Hazards and Earth System Science www.nat-hazards-earth-syst-sci.net 1561-8633 1684-9981 11 3 2011 10.5194/nhess-11-741-2011 http://www.nat-hazards-earth-syst-sci.net/11/741/2011/ http://www.nat-hazards-earth-syst-sci.net/11/741/2011/nhess-11-741-2011.html http://www.nat-hazards-earth-syst-sci.net/11/741/2011/nhess-11-741-2011.pdf 741 749 2011-03-09 GPS water level measurements for Indonesia's Tsunami Early Warning System T. Schöne tschoene@gfz-potsdam.de W. Pandoe I. Mudita S. Roemer J. Illigner C. Zech R. Galas Deutsches GeoForschungsZentrum GFZ, Potsdam, Germany Badan Pengkajian Dan Penerapan Teknologi (BPPT), Jakarta, Indonesia Institut für Geodäsie und Geoinformationstechnik, TU Berlin, Berlin, Germany now at: Norwegian Mapping Authority, Norwegian Hydrographic Service, Stavanger, Norway On Boxing Day 2004, a severe tsunami was generated by a strong earthquake in Northern Sumatra causing a large number of casualties. At this time, neither an offshore buoy network was in place to measure tsunami waves, nor a system to disseminate tsunami warnings to local governmental entities. Since then, buoys have been developed by Indonesia and Germany, complemented by NOAA's Deep-ocean Assessment and Reporting of Tsunamis (DART) buoys, and have been moored offshore Sumatra and Java. The suite of sensors for offshore tsunami detection in Indonesia has been advanced by adding GPS technology for water level measurements. <br><br> The usage of GPS buoys in tsunami warning systems is a relatively new approach. The concept of the German Indonesian Tsunami Early Warning System (GITEWS) (Rudloff et al., 2009) combines GPS technology and ocean bottom pressure (OBP) measurements. 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