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Over the past 10 years, ground-based radar interferometry has become a frequently used technology for determining dynamic deflections of bridge structures induced by vehicle passages. When measuring with only one radar device, the so-called Interpretation Error (EI) considerably rises. When using two radars, it is possible to simultaneously determine, for example, vertical and longitudinal displacements and to eliminate the Interpretation Error. The aim of the article is to establish a suitable strategy for determining dynamic and quasi-static response of bridge structures based on the accuracy analysis of measurement by two radars. The necessary theory for displacements determination by means of two radar devices is presented. This is followed by an analysis of errors when measuring with only one radar. For the first time in the literature, mathematical formulas are derived here for determining the accuracy of the resulting displacements by simultaneous measurement with two radars. The practical examples of bridge structures displacements determination by measuring with two radar devices in the field are presented. The key contribution of the paper is the possibility to estimate and plan in advance the achievable accuracy of the resulting displacements for the given radar configurations in relation to the bridge structure.

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<p><strong>Abstract.</strong> The paper describes possibilities of the relatively new technics &amp;ndash; ground based radar interferometry for precise determining of deformation of structures. Special focus on the horizontal movements of high-rise buildings and on the tower transmitters is presented. The technology of ground based radar interferometry can be used in practice to the contactless determination of deformations of such structures with accuracy up to 0.01&amp;thinsp;mm in real time. It is also possible to capture oscillations of the object with a frequency up to 50&amp;thinsp;Hz in real time. Deformations can be determined simultaneously in multiple places of the object, for example in the case of high-rise buildings it is possible to monitor the horizontal vibration of the whole object at its different height levels intervals of one or more meters. It is possible to detect and determine the compound oscillations that occur in some types of such buildings. This allows to obtain both overall and detailed information about the properties of the structure during its dynamic load e.g. by wind. Then prevent any damage or even disasters in these objects. In addition to the necessary theory basic principles of using radar interferometry for determining of deformation of structures are given. Practical examples of determining of horizontal movements of high-rise building and tower transmitter are also given. The IBIS-S interferometric radar of the Italian IDS manufacturer was used for the measurements.</p>