There are several bright yellow buoys now floating in the Indian Ocean. The German flag is painted on one side, the Indonesian flag on the other.

The buoys have an in-built Global Positioning System (GPS) receiver, connected to a pressure sensor, which lies on the seabed.

The German-led tsunami warning system project involves installing ten such buoys, as well as collecting data from 20 water gauge stations and 100 seismometers.

Jörn Lauterjung from the Geological Research Centre in Potsdam explains how it works: "If a tsunami rolls over the sensor, it will detect the pressure changes. It can measure those things precisely. The buoys are also equipped with GPS sensors, and can measure the changes in sea level."

Central warning centre

Thus any tremor in the Indian Ocean can be detected. The data is automatically transmitted to a central warning centre. A central computer can simulate which direction the tsunami is moving in and how high its walls are.

Then, the experts on duty can decide whether or not to alarm the public. If they decide to do so, the warning can be transmitted by the media or with text messages -- thus being able to reach the most remote fishing village.

"We have made a lot of progress," Lauterjung explained. "Almost all the seismometers have been built. And half of the ground sensors have been installed. Next year, our work will focus on the buoys. We hope to have ten buoys in place by the end of 2008."

The Indonesian president wants to launch the system next autumn. Lauterjung thinks the deadline is tight but is confident they'll make it.

Already a success

The project has already proved to be a success "despite the fact that not all the components have been built yet, the system was able to localise and calculate the magnitude of a series of strong tremors that hit Sumatra’s coast in September this year -- after three and a half minutes,"

"As a result," Lauterjung added, "the Indonesian meteorological and geophysical service was able to give advance warnings within five minutes. That was at least 15 to 20 minutes before the wave hit the coast. You can say that the system has passed the test."

Lauterjung and his colleagues’ work will not come to an end once the technology has been completely installed. They plan to stay in Indonesia at least until 2010 to train local staff in using the advance warning system.