1.1 Exisiting geosensor networks vs. Exupéry network

An excellent example of geosensor network is Volcano Sensorweb project that is currently being developed by Jet Propulsion Laboratory (JPL 2009, Chien et al. 2007, Davies at al. 2006). This project tries to combine field units (containing a seismometer to detect earthquakes, a GPS receiver to point the location and measure subtle ground deformation, an infrared sounder to sense volcanic explosions, and a lightning detector to search for ash cloud formation) with satellite instruments. The field units are packed in a box (size of a microwave oven) that sits on top of a three-legged tripod. The instruments are powered by batteries that can last for a year. Field instruments can communicate among each other but also with EO-1 satellite that carries also a hyperspectral sensor Hyperion. In the case the field instruments sense an increased volcano activity, they order Hyperion to map the thermal anomalies in over 200 channels with a spatial resolution of 10 m. The acquired satellite image then makes possible to automatically reassess the current state of volcano and the importance of each field instrument.

Comparing the definition of the geosensor network to our system we can find an important difference – information from one or more sensors are in our case not automatically used to reconfigure the remainder of the sensors. One of the reasons for that is that we do not have a control over some instruments; e.g., the satellite instruments in our project are controlled by NASA and ESA, thus satellite data are merely processed from some standard data products (e.g. level 1b images) at the data centre (not at the volcano observatory) and then imported into the database. In addition, data from marine instruments cannot be used not even in the near real time because of lack of appropriate wireless communication between the instruments on the ocean bottom and the central station. Nevertheless, as in the geosensor network the backbone of our mobile system is its wireless communication. Most data are then accessed via the seedlink protocol, which forms a unified data portal for a wide variety of commercial digitizers (Hanka et al. 2000). The well defined plug-in concept of seedlink makes it also possible to easily include up to then unknown data sources. All incoming data are then stored in a newly developed, central database – SeisHub.