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<p><strong>Abstract.</strong> The lesser Himalayan region is mostly affected by landslide events occurring due to rainfall, steep slopes and presence of tectonic activity beneath, causing loss of life and property. Some critical zones in the region have encountered recurring landslides over the past and need careful investigation for better planning and rescue operations. This research work presents a geodetic framework comprising multiple sensors to monitor the Sirobagarh landslide in Uttarakhand, India, which is affected by recurring landslides. Three field visits were made to this site for geodetic data collection using Terrestrial Laser Scanner (TLS), Global Navigation Satellite System (GNSS) and Robotic Total Station (RTS). Co-registration and vegetation removal of the TLS scans corresponding to the three visits resulted in generation of three Digital Elevation Models (DEM), which were differenced to estimate temporal movement of the landslide scarp. DEM differences indicate subsidence of the landslide scarp with vertical displacement values ranging from &amp;minus;0.05 to &amp;minus;5.0<span class="thinspace"></span>m. Rainfall induced debris flow is one of the prominent reason for large displacement magnitude (&amp;sim;5<span class="thinspace"></span>m) in the upper landslide scarp. Horizontal displacement estimates obtained by geodetic network analysis of six GNSS stations installed on the study site show movement towards the Alaknanda river. The maximum horizontal and vertical displacement values for the GNSS stations were 0.1305<span class="thinspace"></span>m and &amp;minus;2.1315<span class="thinspace"></span>m respectively. Similar pattern is observed by displacement measurements of RTS target reflectors installed on a retaining wall constructed to arrest the debris flow approaorching the National Highway. The displacement estimates obtained from the sensors applied in this study indicate subsidence of the landslide scarp and surroundings. More time series observations can provide better understanding of the overall deformation process.</p>

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<p><strong>Abstract.</strong> Occurrence of landslide events are common in the lesser Himalayan region which lie in a tectonically active zone with unstable slopes. The Mussoorie region is situated in the lesser Himalayas and is one of most visited tourist sites of the Uttarakhand state. The region is facing social and economic crisis due to the damage caused by multiple landslide events, which requires continuous monitoring for better planning and rescue operations. This study shows the time series analysis of landslide events occurring in the Mussoorie region using the Persistent Scatterer Interferometry (PSI) technique on Sentinel-1 synthetic aperture radar (SAR) images. The processing steps required to process the Sentinel-1 data stacks using both differential SAR interferometry (DInSAR) and PSI are presented. 13 Sentinel-1A C-band interferometric wide swath (IW) images covering a time period of one year are used for PSI processing, resulting in the generation of 12 differential interferograms. The PSI approach extracted 5593 measurement points in the study area. The one dimensional line of sight (1D LOS) time series displacement estimates obtained from PSI processing show a maximum velocity of &amp;minus;55.7<span class="thinspace"></span>mm<span class="thinspace"></span>year^&amp;minus;1 in the radar line of sight (LOS) direction, indicating subsidence. The displacement map further used to characterize the landslide susceptible zones show higher displacement magnitude for areas near Jabarkhet, Bhataghat, Bansagad and Raipur range. Use of more Sentinel-1 images and better DInSAR processing algorithms can improve the displacement estimation and pattern detection.</p>