Arthur Charléty

We investigated the use of passive RFID tags for subsurface localization in challenging environments such as vegetation and snow. A synthetic aperture radar (SAR)-based RFID system was developed, combining high-precision GNSS tracking with phase-based localization methods. Two cost functions were evaluated: a standard complex phasor correlation and a guided phase unwrapping approach. Validation experiments were conducted with tags buried under vegetation layers (hay, bark) and snow covers (dry snow, 1.8-meter-thick wet snowpack). Localization errors were consistently below 5 cm horizontally and 15 cm vertically, even under deep wet snow. The guided phase unwrapping method improved robustness in distorted signal environments at the expense of higher computation time. These results demonstrate the feasibility of passive RFID localization in real-world environmental conditions, opening new perspectives for remote sensing and monitoring applications.

Radio-Frequency Identification (RFID) shows great potential for earth-sciences applications [1], notably for landslide surface monitoring at a high spatio-temporal resolution with long-term robustness to meteorological events (rain, fog, snow) [1,2]. The ability to localize RFID tags using Unmanned Aerial Vehicles (UAV) in a Synthetic Aperture Radar (SAR) approach, would offer new possibilites for monitoring inaccessible terrain, even under vegetation and snow [3].To that end, an onboard measurement system was built that allows Global Positionning (GPS) tracking of an RFID reader antenna, in order to perform real-time SAR measurement acquisition. Three antenna tracking methods were compared.In addition, Markov-Chain Monte-Carlo (MCMC) optimization was used to estimate tag position and characterize the solution, even in non-convex cost function scenarios. Two cost functions were compared, based on different RFID-phase processing approaches.Real-time SAR-RFID localization yielded a centimeter accuracy in the horizontal plane, with lower resolution in the vertical direction. The Post-Processed Kinematics algorithm proved to best fit antenna tracking. The unwrapped-phase cost function provided more convex solutions, at the cost of a lower accuracy compared to the complex-phase cost function. MCMC is computationally efficient in SAR-RFID optimization, with enhanced results concerning the shape and orientation of the main localization errors. [1] Le Breton, Mathieu, et al. "Passive radio-frequency identification ranging, a dense and weather-robust technique for landslide displacement monitoring." Engineering geology 250 (2019): 1-10. [2] Charléty, Arthur, et al. "2D Phase-based RFID localization for on-site landslide monitoring." Remote Sensing 14.15 (2022): 3577. [3] Charléty, Arthur, et al. Towards centimeter precision UAV-RFID localization, in preparation.

The use of Radio-Frequency Identification (RFID) in Earth Sciences has been growing in the recent years, notably for landslide monitoring using phase-of-arrival localization schemes. In this article, an Extended Kalman Filtering approach is presented to exploit RFID phase data for landslide displacement monitoring. The filtering is based on a stochastic Langevin equation for the state-space model, introducing a heuristic coupling based on the mechanical continuity of the landslide material. This helps correct measurement biases and deal with missing data in the tracking of multiple tags. The Kalman state covariance matrix is a useful indicator of the tags localization quality. It can be exploited to discriminate true displacements from multipath-induced artifacts. Phase unwrapping is performed implicitly through the state model.

Passive RFID tags are opening new capabilities of monitoring in geoscience [1], applied to landslide [2-3], snowpack [4] or riverine pebble monitoring. This study investigate the ability to localize passive RFID tags (working at 868 MHz) from the air in harsh conditions met in natural areas outdoors. The tags are localized with the synthetic aperture radar method (SAR) with a mobile reader from above, installed on a rail and equiped with a differential GNSS. The tags are localized either directly on the ground, under a vegetal cover, or under a snow cover, and the localization accuracy is evaluated in each case. This technique opens the possibility to monitor ground displacement even under snow or vegetal coverage, that challenge most of existing displacement measurement techniques. Related studies on the topic :[1] Le Breton, M., Liébault, F., Baillet, L., Charléty, A., Larose, É., Tedjini, S., 2022. Dense and long-term monitoring of earth surface processes with passive RFID—a review. Earth-Science Reviews 234, 104 225. https://doi.org/10.1016/j.earscirev.2022.104225[2] Charléty, A., Le Breton, M., Larose, E., Baillet, L., 2022. 2D Phase-Based RFID Localization for On-Site Landslide Monitoring. Remote Sensing 14, 3 577. https://doi.org/10.3390/rs14153577[3] Le Breton, M., Baillet, L., Larose, E., Rey, E., Benech, P., Jongmans, D., Guyoton, F., Jaboyedoff, M., 2019. Passive radio-frequency identification ranging, a dense and weather-robust technique for landslide displacement monitoring. Engineering Geology 250, 1–10. https://doi.org/10.1016/j.enggeo.2018.12.027[4] Le Breton, M., Larose, É., Baillet, L., Lejeune, Y., van Herwijnen, A., 2022. Monitoring snowpack SWE and temperature using RFID tags as wireless sensors. https://doi.org/10.5194/egusphere-2022-7

Radio-Frequency Identification (RFID) shows great potential for earth-sciences applications [1], notably in landslide surface monitoring at high spatio-temporal resolution [2] with meteorological robustness [3]. Ten 865MHz RFID tags were deployed on part of a landslide (Harmalière) and continuously monitored for 12 months by a station composed of 4 reader antennas. 2D relative localization was performed using a Phase-of-Arrival approach [4,5], and compared with optical reference measurements. The spatio-temporal accuracy of the method allowed for a thorough exploration of the landslides mechanisms during a 6-months period of activity. Laplacian clustering was applied to the RFID data and groups of tags with coherent behavior were identified, allowing a fine description of the kinematic motion of the landslide blocks and various mass transfer mechanisms. Each identified block can be monitored individually. Different deformation zones were highlighted on the monitored zone. The surface movement was initiated by the topmost blocks, transferring after several weeks to the bottom of the monitored zone. This opens the way to building a landslide mechanical model in order to interpret the acquired data. RFID landslide monitoring allows dense observation of ground surface movements at a centimeter scale and with sub-hourly time precision, and new results bring a finer understanding the the landslides inner mechanisms. References :[1] M. Le Breton, F. Liébault, L. Baillet, A. Charléty, E. Larose, and S. Tedjini,“Dense and long-term monitoring of earth surface processes with passiverfid—a review,” Earth-Science Reviews, p. 104225, 2022.[2] M. Le Breton, L. Baillet, E. Larose, E. Rey, P. Benech, D. Jongmans, F. Guy-oton, and M. Jaboyedoff, “Passive radio-frequency identification ranging, adense and weather-robust technique for landslide displacement monitoring,”Engineering geology, vol. 250, pp. 1–10, 2019.[3] M. Le Breton, L. Baillet, E. Larose, E. Rey, P. Benech, D. Jongmans, andF. Guyoton, “Outdoor uhf rfid: Phase stabilization for real-world appli-cations,” IEEE Journal of Radio Frequency Identification, vol. 1, no. 4,pp. 279–290, 2017[4] A. Charléty, M. Le Breton, E. Larose, and L. Baillet, “2d phase-based rfid lo-calization for on-site landslide monitoring,” Remote Sensing, vol. 14, no. 15,p. 3577, 2022. [5] P. V. Nikitin, R. Martinez, S. Ramamurthy, H. Leland, G. Spiess, andK. Rao, “Phase based spatial identification of uhf rfid tags,” in 2010 IEEEInternational Conference on RFID (IEEE RFID 2010), pp. 102–109, IEEE,2

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.

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 spatiotemporal 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.

Passive Radio-Frequency Identification (RFID) has been used to monitor landslide displacement since approximately 5 years. This method allows soil displacement estimation at a high spatio-temporal resolution, and at a relatively low cost. In perspective of the previous years, this paper proposes to summarize the various challenges encountered with the long-term outdoor RFID localization method, and presents solutions that were implemented to overcome these challenges. Finally, displacement results from three monitored sites are shown in order to validate the implemented solutions.

Passive radio-frequency identification (RFID) was recently used to monitor landslide displacement at a high spatio-temporal resolution but only measured 1D displacement. This study demonstrates the tracking of 2D displacements, using an array of antennas connected to an RFID interrogator. Ten tags were deployed on a landslide for 12 months and 2D relative localization was performed using a phase-of-arrival approach. A period of landslide activity was monitored through RFID and displacements were confirmed by reference measurements. The tags showed displacements of up to 1.2 m over the monitored period. The centimeter-scale accuracy of the technique was confirmed experimentally and theoretically for horizontal localization by developing a measurement model that included antenna and tag positions, as well as multipath interference. This study confirms that 2D landslide displacement tracking with RFID is feasible at relatively low instrumental and maintenance cost.

Radio-Frequency Identification (RFID) shows great potential for earth-sciences applications, notably in landslide surface monitoring at high spatio-temporal resolution [1] with meteorological robustness [2]. Ten 865MHzRFID tags were deployed on part of a landslide and continuously moni-tored for 8 months by a station composed of 4 reader antennas. 2D rela-tive localization was performed using a Phase-of-Arrival approach [3], andcompared with optical reference measurements. The centimeter-scale ac-curacy of this technique was confirmed theoretically by developing a mea-surement model that includes multipath interference and system sensitiv-ity kernel. Although horizontal localization shows promising results, ver-tical displacement monitoring presents intrinsic error sources that greatlydecrease accuracy in this direction. This study confirms that 2D landslidedisplacement tracking is feasible at relatively low station and maintenancecost (Charlety et al.,2021, submitted).References[1] M. Le Breton, L. Baillet, E. Larose, E. Rey, P. Benech, D. Jongmans, F. Guy-oton, and M. Jaboyedoff, “Passive radio-frequency identification ranging, adense and weather-robust technique for landslide displacement monitoring,”Engineering geology, vol. 250, pp. 1–10, 2019.[2] M. Le Breton, L. Baillet, E. Larose, E. Rey, P. Benech, D. Jongmans, andF. Guyoton, “Outdoor uhf rfid: Phase stabilization for real-world appli-cations,” IEEE Journal of Radio Frequency Identification, vol. 1, no. 4,pp. 279–290, 2017