Reliability and precision of a network for monitoring very slow movements with a Total Station

This paper describes the monitoring system planned to measure the displace-ments of an extremely slow landslide in an alpine glacial valley in Northern Italy. Because of the smallness of the displacements, normally less than 1 cm/year, great attention has been paid to evaluate the reliability of the measurements by evaluating their precision and accuracy. For this purpose it was essential to make the system redundant by measuring the displacements with at least two different techniques: the inclinometers to monitor the subsurface displacements and the Total Station for measuring the surface displacements. With the increase of redundancy of the measures, there are more information to describe the landslide in terms of displacements, directions and rate, both superficial and deep. In this way, movements are better investigated and it is possible to highlight eventual disagree between the different techniques of measurement and improve the result’s accuracy. The paper focuses mainly on the characteristics of the net-work used with the Total Station, in order to define how they affect the precision and accuracy of the measurements. Thus, the aim of this research has been to derive some conclusions about the op-timal monitoring surveying network in terms of reliability and precision, compati-ble with the type of slope movements and the morphology of the site. The strategies of elaboration and results obtained are presented in this paper.