Bridges, before putting into use, are subjected to test loads in order to their acceptance. According
to Polish Standards, the aim of loads is to verify the computational model designed for the construction
and to confirm the safety margins. Such tests are designed and executed under static and dynamic loads. In
the case of static loads conventional surveying techniques are widely applied, while for dynamic loads the
measurements using accelerometers are typically provided. These methods are characterized by significant
limitations which include i.a. low sampling rate (measurements performed by total stations, digital levels,
GPS receivers) and discrete (limited to points) nature of measurement (a set of accelerometers). The authors
present the results of comparing the measurements carried out during test loads of a cable-stayed bridge, performed
using classical measurement methods and ground-based radar interferometer. This innovative measuring
device operates on the basis of stepped-frequency continuous wave modulation and microwave interferometry
technique. It allows to determine deformation and vibration frequency of the object through a noninvasive
observation of its behaviour at a frequency of up to 200 Hz.