Proceeding of the Joint International Symposium on Deformatuon Monitoring. 2-4 November, 2011. Hong Kong. China. Report. This work presents the development of a methodology for using the Global Positioning System (GPS) as a tool for Civil Engineering to monitor the vibrations of large road structures, notably the bridges. To be characterized as a structural tool a method was developed and tested which is based upon the interferometry principle. The method uses the L1 carrier phase that needs to be collected from only two satellites and this particular characteristic makes it different to the methods used in other studies. The structure's vibrations also defined by oscillations or areas of dynamic displacement characterized by the measuring of the extent of the displacement during the specific time in which it occurs and its frequency. The method included the use of an electro-mechanical oscillator specially projected to receive the GPS antenna which allows the calibration of the extent and frequency of the oscillation present in the structures tested. The method was assessed by means of field tests carried out on two structures: a cable-stayed wooden footbridge and a cable-stayed bridge as described below. The efforts to develop a method for using the GPS for the dynamic monitoring of bridges is based upon the value of the dynamic analysis of structures that allow an analysis of the real state of preservation of structure (independent of out appearance), an estimate of the extent of its useful life and the establishment of economic solutions for its recuperation in a way which can extend its durability.