First Test of Mixed (Single- & Dual-Frequency) GPS Receivers
on Papandayan, February 2000

In mid February 2000 Craig Roberts and Volker Janssen went to West Java, Indonesia, for four weeks. They continued their work on the volcano deformation monitoring system that Craig had deployed on Gunung Papandayan in July 1999. For over a year plans had been made to also set up a ÔfiducialÕ network equipped with dual-frequency receivers surrounding the deformation zone, and to simultaneously operate the single-frequency network on the volcano.

The fiducial network consisted of three Leica CRS1000 dual-frequency GPS receivers surrounding the deformation zone around the volcano. It's purpose was to generate empirical correction terms to account for error sources such as orbit bias, tropospheric delay and ionospheric delay across this local area. These correction terms can then be applied to the inner single-frequency network to improve accuracy (a strategy that is being used on the Singapore multi-base station network).

With the help of our collaboraters at the Institute of Technology Bandung (ITB) and the Volcanological Survey of Indonesia (VSI) the fiducial three GPS stations were established in Bandung, Galunggung and Pameungpeuk. The latter two sites were temporary stations, the monuments for which were fashioned by local craftsmen (see below)!