Landslides activity
Satellite(s)Sentinel-2, Sentinel-1, TerraSAR-X | Monitoring elementSAR backscatter, land surface reflectance. |
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Description techniqueA range of remote sensing applications for landslide activity are available. Optical remote sensing has been mainly used to generate landslide inventories, through application of long time series to both spatial and temporal understanding of landslide activity (Behling et al., 2015). Recent research also suggests that Sentinel-2 can be used to monitor for land movement occurring prior to landslide activity via mapping horizontal displacement using image correlation across a time series, though only large landslides may be detected due to sensor resolution and highly accurate rectification is required (Lacroix et al., 2018). A significant number of studies utilize Synthetic Aperture Radar sensors for Interferometry (InSAR), with Sentinel-1 data favoured in recent years due its rapid revisit and open access (Raspini et al, 2018). Interferometry exploits the phase difference between two SAR observations to extract highly detailed distance observations. These studies exploit this to detect changes in ground position (surface deformation) to detect landslide activity prior to mass slips (e.g. Czikhardt et al, 2017, Barra et al., 2016). | Accuracy / ResolutionVariable spatial and temporal resolution according to sensors. |
Case studyBy using a combination of spectral bands sensitive to vegetation cover, Behling et al., 2015 show that the rapid change in spectra sensitive to vegetation pre and post landslide activity can be used to resolve the location, extent and date at which the event occurred. By utilising a time series of data, Raspini et al (2018) demonstrate how Sentinel-1 can be used in a continuous manner to monitor for ground displacement preceding landslides in Central Italy while Czikhardt et al (2017) demonstrate that InSAR data (derived deformation measurements) relates well to field measurements in Slovakia. | |
Benefits
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Applicability for NorthlandYes, possibly. •Applications based on optical data remain a challenging prospect in Northland as a result of the persistent cloud. Testing would be required to determine the applicability of SAR based applications within Northland, but these workflows have been successfully applied in similar environments. Techniques applying optical data will be limited in coverage and temporal granularity by the persistent cloud cover in the region, particularly during the winter months. Mature cloud-masking techniques are directly available for open access multispectral data (e.g. Landsat and Sentinel-2). When using commercial data, care must be taken to ensure that there is sufficiently cloud free imagery available, as cloud masking is not as mature and ordering a large volume of imagery to ensure complete cloud free coverage between multiple observations can become cost prohibitive. | |
Publications references Zhao, C. and Lu, Z., 2018. Remote sensing of landslides—A review. Remote Sensing, 10(2), p.279. https://www.mdpi.com/2072-4292/10/2/279/htm
https://www.sciencedirect.com/science/article/pii/S0034425718301433
https://www.tandfonline.com/doi/full/10.1080/19475705.2016.1171258
https://www.nature.com/articles/s41598-018-25369-w
https://www.mdpi.com/2076-3263/7/3/87/pdf/1
https://www.sciencedirect.com/science/article/pii/S0034425716302747
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Other comments or informationUsage of cloud based services such as Google Earth Engine (GEE) can offer a simplified point of access for Sentinel-1 data by providing datasets which have already had extensive pre-processing, but the complex data required for InSAR is currently not available. |