Investigation of the accuracy of GNSS-vector measurements during the deformation monitoring of engineering structures: case study in tested network

Purpose. The aim of the investigation is optimization monitoring of spatial displacements by GNSS and selection of minimal intervals of GNSS observations with given accuracy parameters. Methodology. For simulate the monitoring process on a real object tested network GNSS vectors with different lengths were installed. The network consisted of 4 points where two-frequency GNSS receivers were installed. At one of the points for deformation simulation, a specially designed device was installed which allowed to change the GNSS antenna position with high accuracy. The reference stations SULP and NTEH as well as the JAHT station, which was installed on the pillar of the 2nd academic building of the Lviv Polytechnic National University, was chosen as a geodetic reference point. Continuous observations were conducted in static mode from January 25 to February 8, 2017 inclusive. During 15 days of observations, the antenna was displaced in a horizontal plane by means of a deformation simulation device. In total, 4 displacements were made during the investigation period. To detect model deformations, single vectors with 1, 3 and 6 hours observation intervals were used. These results were compared with the results of network adjustment.  Results The observations data were processed in the software Leica Geo Office 8.2. According to the results of the observations, the accuracy of the detection of  antenna spatial displacements for the various lengths of the vectors and the duration of the GNSS observations were calculated. Experimental studies carried out for vectors up to 2 km show that to achieve the accuracy of the deformation determination at a level of 3 mm in the horizontal plane and 5 mm in height that there was enough 1 hour interval observations with the data sampling rate 1 s. Practical significance. The obtained results in the future can be used as recommendations in the design and construction of automated systems for monitoring complex engineering structures.