Investigations Over Using Mirrors and Prisms in Geodetic Monitoring of Building Structures

Abstract

The paper describes research works over displacement monitoring system based on distance measurements, which could allow the determination of movements of inaccessible points located on the building structure. Due to the dispersion of tested points over large object as well as to existing difficulties with visibility a method has been elaborated that gives access to points via additional optical elements -flat mirrors and/or rectangular prisms. In order to protect against external influences the reflecting area of the mirror and back wall of the prism were Al+SiO 2 -coated. Two optical devices for laser measurements have been planned and purchased for tests. They have been installed in two-hinge brackets to be able to turn laser beam toward the prism mounted at measured place. Flexible research stand was mounted and two tests were performed for the distance up to almost 30 m: a 100-fold and 10-fold with varying distances. Analysis of the results showed that the designed set of devices allows the cyclic displacement measurement of multiple points located within 50 m from the instrument with an accuracy not worse than ±1 mm. It has been concluded that proposed approach based on distance measurements can be expanded by angles what should give the opportunity to determine three components of the displacement of test points. It is planned to focus further works on the use of the set: robotic total station + mirrors + reflective targets and control its stability in spatial displacement surveys to inaccessible points located on engineering structures or buildings.