Global Positioning System (GPS) technology with high sampling rates (~10 sps) allows scientifically justified and economically feasible dynamic measurements of relative displacements of long-period structures ― otherwise difficult to measure directly by other means, such as the most commonly used accelerometers that require post-processing including double integration. We describe an experiment whereby the displacement responses of a simulated tall building are measured clearly and accurately in real-time. We also describe successful, permanent deployment of GPS units at the roof of buildings in an urban environment. To the authors' best knowledge, this is the first, working, permanent and pioneering deployment of GPS units (in the world) for dynamic monitoring of long-period structures. Data recorded manually from such a deployment during a rather windy day is analyzed to determine the structural characteristics and applicable coherencies at identified frequencies. Such measurements can be used to assess average drift ratios and changes in dynamic characteristics, and therefore can be used by engineers and building owners or managers to assess the building performance during extreme motions caused by earthquakes and strong winds. By establishing threshold displacements or drift ratios and identifying changing dynamic characteristics, procedures can be developed to use such information to secure public safety and/or take steps to improve the performance of the building.
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