A document by PRITI GIROHI. Click on the document to view its contents.

A document by PRITI GIROHI. Click on the document to view its contents.

Openly accessible space-borne lidar, ICESat-2 datasets along with Pleiades stereo datasets provide a unique opportunity for estimation and monitoring of fragile sites in relatively inaccessible complex terrain for their changes in elevation and state. Two sets of over 100 lidar points (footprints) from ICESat-2 Track ID: 1354, dated 27 March 2019 were chosen in the flood-impacted Rishiganga and Dhauliganga valleys, i.e. at the place of the rock slide and a confluence Junction on the downstream side towards the severely affected Raini Village. These two locations depict the large-scale changes that occurred due to the flash flood initiated by the rockfall on 7th February 2021. The pre-and post- datasets from Google Earth optical images depict the large variations that occurred due to the event. Digital elevation model generated from Pleiades stereo datasets acquired on 10th February 2021 (post-event), is used for analysis with ICESat-2 datasets (pre-event). Before the event at the analyzed junction location, there was a width of about 30m channel with boulders and had tree-covered surrounding slopes. After the event lot of mud and debris have accumulated in a width of about 300 m without tree cover. The trees got unearthed in the processes involved in the event. The analysis shows a clear sign of erosion on the banks and the accumulation of debris along the river channel as well. The analysis depicted an accumulation of debris that raised the elevation from 0.1m to 44.86m at places with an average of 11.34m. Whereas the erosion varies from 0.15m - 15.76m with an average of 4.85m, mainly on the eroded river banks.

Vivo 1606 model is used for the study of standalone use of smartphone as a positioning device with FM supported location (Assisted- GNSS) for GPS, GLONASS, BeiDou. The observations were collected at every 5-minute interval for the analysis. The sessions were divided into three shifts morning, afternoon, and evening to check the accuracy in real time static mode. Mobile topographer app was used for capturing WGS-84 geographic coordinates having horizontal and vertical position with time in an urban environment to analyze which time of a day is good and till what time one can take GPS reading to get the minimum errors using smartphone. It is found that the positional dilution of precision (PDOP) stabilizes in about 35 minutes and minimizes at a value 0.2. The observations beyond have minor changes, so the position at 35 minutes has been used as reference for evaluation of statistical parameters. The real time observations of horizontal, vertical, and positional accuracy seem to increase with time as the PDOP, HDOP, VDOP values decrease i.e. improves with time. It has been observed that, RMSE of PDOP is 0.0485 and HDOP is 0.029 during afternoon is higher as compared to morning and evening values. The study suggest that the preference of survey shall be in the order: morning, evening and afternoon, which may further depend on the season at time. The survey during noon in summers can give much higher values of PDOP and thus the survey can be carried out during morning and evening times preferably.