Dynamic Monitoring of Structures at the Millimeter Level: GPS versus Displacement Transducers and Accelerometers … A Summary

Ana Paula C. Larocca, Ricardo E. Schaal, Marcelo C. Santos, Richard B. Langley and Don Kim

Abstract:	The Global Positioning System is becoming a leading technology for monitoring dynamic displacements of structures, notably large bridges and tall buildings. These structures have been monitored in the past by geotechnical instruments such as accelerometers and displacement transducers. In this paper we compare the precision and accuracy of displacements from GPS data with values from a displacement transducer and an accelerometer. In order to compare GPS with a displacement transducer, an experiment was conducted on a footbridge to measure the amplitude and frequency of displacements induced by pedestrians. For comparing the performance of GPS with values from an accelerometer, an electro-mechanical oscillator (EMO) was used to apply the same periodic vertical displacements to both instruments. In this paper, we present a brief summary of the methodology used and the test results. The Phase Residual Method (PRM) was used to determine the displacements as sensed by the GPS antenna. An indication of the precision and accuracy of this method is shown from the analysis of results obtained from the different techniques. The uncertainty of amplitude determinations was estimated as being around 1 mm. GPS can be considered more precise than many accelerometers for detecting the frequency of periodic oscillations in part due to the higher precision of the raw GPS measurements and to the higher-precision clocking of the data.
Published in:	Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005) September 13 - 16, 2005 Long Beach Convention Center Long Beach, CA
Pages:	1957 - 1960
Cite this article:	Larocca, Ana Paula C., Schaal, Ricardo E., Santos, Marcelo C., Langley, Richard B., Kim, Don, "Dynamic Monitoring of Structures at the Millimeter Level: GPS versus Displacement Transducers and Accelerometers … A Summary," Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005), Long Beach, CA, September 2005, pp. 1957-1960.
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