GNSS data for monitoring some movements on the island of Ischia

The aim of the present work is to present the first results of the study of integrated techniques for monitoring slow movements. In particular, the differential plano-altimetric accuracy characteristics of some sensors based on GPS/GNSS technology that use innovative proprietary algorithms are being tested; the high accuracy expected from these sensors requires a careful choice of comparison techniques, in particular SAR techniques are considered to be among the few comparable techniques. Currently, two of these sensors have already been installed at sites affected by slow movements, the nature of which is still being debated within the scientific community. These sites are in the territory of the municipality of Forio (Na) and close to the epicentre of the 2017 seismic event with epicentre in the municipality of Casamicciola. The movements under study (already observed by other researchers) are generally estimated to be in the order of a few centimetres per year therefore their monitoring and/or the possible establishment of an early warning system require millimetre or (possibly) sub-millimetre accuracies. Such accuracies are difficult (millimetric) or impossible (sub-millimetric) to obtain with ‘classic’ differential GPS/GNSS techniques, since the accuracies of these techniques are generally very close to the expected values of the movements under study. The study below will illustrate the first results on some time series of data obtained from receivers in classical post-processing mode that will be one of the benchmarks for the innovative technique.