L1 GPS as Tool for Monitoring the Dynamic Behavior of Large Bridges

Abstract

In 1973 the JPO (Joint Program Office) subjected to United States Air Force received the missionof Department of Defense for implanting, developing, testing and use a spatial positioningsystem for military applications and able to calculated coordinates and guide missilesaccording to the project “Star Wars”.The Global Positioning System is fruit of those studies which became able to use the L bandof carrier phase (frequency microwaves around 1 up to 3 Ghz and wave length close to 23 cm)for calculating the spatial trilateration. Therefore, in 1978 began the launch of the first NAV‐STAR (Navigation Satellite with Time and Ranging) satellites – the begging of GPS as is knowntoday. Due to the high cost of project and as the MIT confirmed by itself the excellence on civilapplications (geodesy, topography, navigation, digital modeling, simulators), the AmericanCongress, with the acquiescence of the U.S. President, pressed the Pentagon to open theNAVSTAR system for civil use and other countries. However, only from the 90s is that theGPS became popular. This was a result of technological advance in the micro-computers fieldallowing the trackers manufacturers to produce the GPS receivers that processed in thereceiver, the codes of the received signals.In this context, from the end of the 80´s, the technology of Global Positioning System, untilthen, used to conduct surveys of areas, deploy geodetic networks, manage resources, trackfleets of vehicles, ships, achieve the control of displacements of structures under static load,etc. began to be used to characterize the dynamic displacement of large structures, earthquakesand so, it was being considered as a tool to extract the values of frequency and amplitude of