title: Low-Cost GNSS Receivers for Local Monitoring: Experimental Simulation, and Analysis of Displacements.
abstract: The geodetic monitoring of local displacements and deformations is often needed for civil engineering structures and natural phenomena like, for example, landslides. A local permanent GNSS (Global Navigation Satellite Systems) network can be installed: receiver positions in the interest area are estimated and monitored with respect to reference stations. Usually, GNSS geodetic receivers are adopted and provide results with accuracies at the millimeter level: however, they are very expensive and the initial cost and the risk of damage and loss can discourage this approach. In this paper the accuracy and the reliability of low-cost u-blox GNSS receivers are experimentally investigated for local monitoring. Two experiments are analyzed. In the first, a baseline (65 m long) between one geodetic reference receiver and one u-blox is continuously observed for one week: the data are processed by hourly sessions and the results provide comparisons between two processing packages and a preliminary accuracy assessment. Then, a network composed of one geodetic and two u-blox receivers is set up. One u-blox is installed on a device (slide) that allows to apply controlled displacements. The geodetic and the other u-blox (at about 130 m) act as references. The experiment lasts about two weeks. The data are again processed by hourly sessions. The estimated displacements of the u-blox on the slide are analyzed and compared with the imposed displacements. All of the results are encouraging: in the first experiment the standard deviations of the residuals are smaller than 5 mm both in the horizontal and vertical; in the second, they are slightly worse but still satisfactory (5 mm in the horizontal and 13 mm in vertical) and the imposed displacements are almost correctly identified.
authors.affiliation: Department of Civil and Environmental Engineering, Politecnico di Milano, Como 22100, Italy. ludovico.biagi@polimi.it.
authors.forename: Ludovico
authors.initials: L
authors.lastname: Biagi
authors.affiliation: Department of Civil and Environmental Engineering, Politecnico di Milano, Como 22100, Italy. florincatalin.grec@polimi.it.
authors.forename: Florin Cătălin
authors.initials: FC
authors.lastname: Grec
authors.affiliation: Department of Civil and Environmental Engineering, Politecnico di Milano, Como 22100, Italy. marco.negretti@polimi.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Negretti
keywords: displacements analysis; landslide monitoring; low-cost GNSS receivers; static surveying; time series analysis; u-blox