RFID Landslide Monitoring: Long-Term Outdoor Signal Processing and Phase Unwrapping

Localization of passive Radio-Frequency Identification (RFID) tags has been used to monitor landslide surface displacement since 5 years. This method, applied on slow displacements lower than 1cm per day, allows a high spatio-temporal resolution at a relatively low cost. With the feedback of the previous years, this paper proposes to summarize the various challenges encountered with the long-term outdoor RFID localization method, and presents data-processing solutions that were implemented to overcome these challenges. We propose a complex-smoothing unwrapping algorithm, a multi-frequency merging operation, as well as multi-tag and multi-antenna phase combining method. The concept of an unwrapping reference guide is presented and applied with groups of tags showing coherent displacements, or with absolute reference measurements. These approaches allow a higher data availability up to 38% for one site over multiple years, and a better phase unwrapping. Earth surface displacement monitoring with RFID proves to be a robust and accurate solution, with four equipped sites across France and Switzerland.

Automated summary

This paper summarizes the use of passive RFID tags for monitoring landslide surface displacement over the past five years. This method is effective for slow displacements under 1cm per day and offers high spatio-temporal resolution at a relatively low cost. The paper proposes data-processing solutions, including a complex-smoothing unwrapping algorithm, multi-frequency merging operation, and multi-tag and multi-antenna phase combining method, to overcome challenges encountered with long-term outdoor RFID localization. These approaches significantly improve data availability and phase unwrapping, making RFID-based earth surface displacement monitoring a robust and accurate solution.