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2 Outline Background on Landslides Landslides Prediction System Architecture Solution Evaluation

3 Landslides A landslide is an catastrophic event where a block of earthen mass slides downhill. Cause significant loss of life and billions of dollars each year.

4 Landslides Prediction Although a basic understanding of the landslides is available, system that predict the occurrence of a landslide do NOT exist. Why? –The lack of field measurements over large temporal and spatial scales.

5 Landslides Prediction The development of a landslide is a temporal process –takes as long as a year to develop –Movement speed, several cm per month Landslides are spatial in nature. –Position –Movement direction This paper propose a WSN to detect the early signals preceding a landslide.

6 System Architecture Sensor Column –Geophone –Strain Gauge –Pore Pressure Transducer –…

7 System Architecture Deployment –A network of sensor columns –Placed in vertical holes drilled over the hill surface Using sensor columns to detect movements

8 Solution Outline Geophones estimate displacement d ij (t) Based on distance matrix D=[d ij (t)] –Detection Determine whether slip surface has formed –Classification Estimate subset of sensors that moved –Localization Compute location of slip surface

9 Example Detection & Classification & Localization

10 Detection Use strain gauges on each sensor column –Can measure changes in their length due to deformation

11 Classification Determine which sensors are above and below the slip surface Basic principles: Distance between two nodes –Below the slip surface should not change –Across the slip surface is likely to change –Above the slip surface would see a small change –The nodes located closest to the known rigid part are unlikely to move. (anchor nodes)

12 Classification Voting Algorithm –Note state: {0, 1, U} –Initially: anchors=0, rest=U –Repeat until all nodes classified Update node i’s state based on votes from neighbors j –If j in U, no vote –If Δd ij =0, vote is equal to j’s state –If Δd ij ≠0, vote is equal to complement of j’s state

13 Localization Localize moved nodes using trilateration Slip surface estimation

14 Evaluation Evaluation metrics –Average and std. dev of localization error –Max. distance between actual and estimated slip plane Abstract network model –Communications are error-free –Nodes do not fail

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16 Summary Propose a WSN for the prediction of landslides Design a system to detect the early signals preceding a landslides. Prediction Finite Element Analysis Simple Measurement Temporal & Spatial Measurement Civil Engineering WSN

17 Remarks Localization for a specific application (landslides prediction) –NOT for general purpose. Localization for a group of sensors (sensors above slip surface) –NOT for a single sensor node. Localization for moving sensor –although there is only a little movement

18 Thanks!