Dynamic testing of historic towers using an interferometric radar from an unstable measurement position

Interferometric radar is a rather popular equipment able to remotely perform dynamic testing of large structures (towers, bridges, buildings..) by detecting the relative displacement in the line of sight between the radar and geometric discontinuities in the engineering structure under test. This technique has been demonstrated effective when the radar is positioned at ground on a stable position. Unfortunately there are practical cases for which a suitable stable position is not available. This is the case of the towers of San Gimignano (Italy) that are embedded in the narrow streets of the old town. A solution to monitor the towers is to install the radar on the top of a tower, which is located in a central position of the town. The tower is not a stable arrangement for the radar and in this paper the authors propose and test the use of an accelerometer fixed to the radar head for detecting and removing its own movement.