Continuous monitoring of active earth flow by means of an integrated GPS-automatic total station approach

The research deals with the integration of surface displacement measurements obtained using geodetic and topographic instruments such as GPS, automatic total station and inclinometer sensor in a large-scale active earth flow. The landslide, located in the northern Apennine of Italy, damaged roads and endangered houses during a sequence of reactivations in 2001, 2005 and 2007. Monitoring has been performed by means of: an automatic total station, coupled with inclinometer sensor, measuring about 40 prisms located in the landslide to a maximum distance of 1.650 km; one double-frequency GPS receiver connects in streaming by wireless communication with 4 single-frequency GPS in side the flow. Until December 2007 the monitoring network was operated with periodic static surveyings followed by the data post-processing; while since March 2008 the total station system and GPS were automated in order to allow continuous data acquisition and near-real-time data processing. The monitoring network has been able to cope with displacement rates ranging from millimetres to metres per day, a performance not achieved by borehole systems operated in the slope, such as in-place inclinometers, that were damaged when displacements exceeded some decimetres. The data so far collected, integrated with geomorphic, geologic and borehole data, allowed the complex spatial and temporal pattern of slope movements to be tracked and the relationships between rainfall pattern and acceleration-deceleration phases to be highlighted.