How effective is monitoring concrete dams with GNSS in 3D mode?

Abstract

Since GNSS is a three-dimensional satellite positioning and navigation system, however, it is unusual to monitor dams in the altimetric component with this system, but only in the two horizontal components. Thus, the third component of three-dimensional positioning guaranteed by GNSS is wasted. There are two main reasons to justify this practice: firstly, because vertical positioning with GNSS is around two to three times less precise than horizontal positioning; and secondly, because spirit levelling allows for very precise and still very expedient vertical positioning, although it is very difficult to implement automatically. The aim of this work is to quantify the effectiveness of GNSS in 3D monitoring of concrete dams, based on Portuguese experience of monitoring these structures with such a system.