Volcanoes and Satellites

Volcanoes are an awesome display of Nature's power. In addition, volcanic explosions are often very destructive events having a massive impact on the natural and human environment. Volcanoes pose a particularly significant threat to the country of Indonesia, which is home to 129 active volcanoes. 18 million Indonesians, 10% of the total population, live in areas under threat from volcanic eruptions. SNAP, in partnership with the Volcanology Survey of Indonesia (VSI) and the Department of Geodetic Engineering, at the Institute of Technology Bandung (ITB), worked to develop a GPS-based volcano monitoring system which is an improvement on existing technologies.

A variety of technologies are used to monitor the activity of a volcano. Although the most extensively used method is seismic, increasing use is being made of geodetic techniques which monitor the horizontal and vertical surface deformation of the volcano flanks and summit. The pattern and rate of surface movement can reveal the depth and rate of pressure increase within the underlying magma reservoir, an important precursor to eruptions. The problem is that routine geodetic measurements are made at only a few dozen of the world's 600 or so active volcanoes.

Ground deformation is a phenomenon ideally suited for study using GPS. GPS systems measure the change in length (as well as height difference and orientation) of baselines connecting receivers in a carefully monumented ground network established across the volcano by repeatedly measuring the same baseline components on a regular basis. A network of permanent, continuously operated GPS stations can be deployed to mitigate natural hazards such as due to sudden volcanic activity through the continuous measurement of a deformation, which if it were to exceed some predefined amount could alert the appropriate authorities.

It is a sobering fact that the total hardware cost for each station in a conventional GPS system is of the order of US$20-30K. At this level of capital investment only two or three such GPS networks could realistically be financed by government or research organisations in many countries. For Indonesia, with the world's largest number of active volcanoes, the GPS technology for volcano monitoring on a continuous basis is simply too expensive to invest in. The SNAP design was significantly cheaper than the conventional GPS systems, and is based on low-cost GPS hardware, integrated within hardened aluminium boxes with an embedded PC and UHF radio for transmitting the data to a master station. With such a design as many as ten receiver systems can be deployed, with all the data processing being carried out on a PC at the master station, for little more than the cost of just of one off-the-shelf geodetic (dual-frequency) GPS receiver. However, developing an automatic GPS array system, and associated analysis software system, for monitoring the deformation zone around a volcano was a major engineering and software challenge.

Two PhD research projects were completed for this project, one by Craig Roberts and the other by Volker Janssen.

The package of GPS, computing and radio gear used for each of the volcano monitor stations.

Three ARC grants have supported the work, the most recent being awarded in 1998. The aim was to install a pilot network of four GPS receivers on the Indonesian volcano Gunung Papandayan in 1999. One will function as a master station and will be located at a VSI observatory and the other three were installed on the volcano itself.

 

Location of the volcano in east Java, Indonesia.

 

Reconnaissance in August 1998 ...

Prototype system installed in July 1999 ...

Prototype (single & Dual-frequency) system tested in February 2000 ...

Prototype (single & Dual-frequency) system tested in July 2001 ...

More photographs ...