Investigating the Potential of LPS in Structural Health Monitoring

In view of reconstructing the stress and strain fields inside the medium, non contact displacement sensors, like GPS (Global Positioning System) sensors, are preferable. Nevertheless, GPS has shortcomings in dense urban areas and inside the building, where it cannot deliver equal precision in all position components at any time. These remarks suggest to move to the study of Local Positioning Systems (LPS). In this paper, the principles of several distance measurement procedure are reviewed. Then, several ways used to reflect signal propagation time precisely are investigated. The available solutions, which include the carrier phase measurement, are discussed mainly in terms of measurement principle, measurement precision and covering range. At last, the ambiguity problem occurred in carrier phase measurement are covered.