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Utilization of Satellite Geophysical Data as Precursors for Earthquake Monitoring
Published in Ramesh P. Singh, Darius Bartlett, Natural Hazards, 2018
A geoid is an equipotential surface over the Earth, and details of geoid undulation over the Indian land mass have been discussed by Moritz (1980) and Majumdar et al. (2001). EGM96 geoid data have been extensively used for geoid surface calculation over land. Theoretical geoids are converted to gravity using the following technique.
Correction of global digital elevation models in forested areas using an artificial neural network-based method with the consideration of spatial autocorrelation
Published in International Journal of Digital Earth, 2023
Yanyan Li, Linye Li, Chuanfa Chen, Yan Liu
SRTM is a cooperative project sponsored by the National Aeronautics and Space Administration (NASA) and the National Geospatial-Intelligence Agency (NGA) (Farr et al. 2007). It was launched in February 2000 for 11 days and collected topographic data between 60° N and 56° S latitude using InSAR with C- and X-band. Thus, SRTM data was collected in winter in the northern hemisphere when the deciduous trees have defoliated. At present, many versions of C-band SRTM DEMs have been released, and the most popular version (V4.1) was produced by the Consortium for Spatial Information using a void-filling interpolation method (Reuter, Nelson, and Jarvis 2007). The specified vertical accuracy of the 1 arc-second SRTM (SRTM1) at 90% confidence level is 16 m and horizontal accuracy is 20 m (Rodriguez, Morris, and Belz 2006). Becek (2008) reported that the root mean square error (RMSE) of SRTM was less than 2 m when compared with runway elevation data around the world. The horizontal datum of SRTM is the World Geodetic System 1984 (WGS84), and the vertical datum is the Earth Gravitational Model of 1996 (EGM96). SRTM1 has been freely available worldwide since September 2014 (González-Moradas and Viveen 2020). SRTM1 was used in this study, which was downloaded from CGIAR-CSI (http://srtm.csi.cgiar.org/).
Geomorphic mapping and analysis of neotectonic structures in the piedmont alluvial zone of Haryana state, NW-India: a remote-sensing and GPR based approach
Published in Geomatics, Natural Hazards and Risk, 2023
Harsh Kumar, R. S. Chatterjee, R. C. Patel, Abhishek Rawat, Somalin Nath
In this study we used different types of multispectral satellite images, which have different resolution and optical properties. The variation in the resolution of the selected images would cause uncertainty in the analysis and hence resampled to the same resolution. The processed images are Resourcesat LISS-III (23.5 m), Landsat 4-5 TM, Landsat 8 OLI (30 m) and Cartosat-1 PAN ortho image (2.5 m). A unified False Colour Composite (FCC) image for the study area was prepared by mosaicking different Landsat TM FCC images. Landsat multispectral images with a spatial resolution of 30 m were used for studying dynamic changes in the drainage system. Geological data such as lithology, geomorphology and structures (faults/lineaments) were collected from the BHUKOSH online portal of GSI (http://bhukosh.gsi.gov.in/Bhukosh/MapViewer.aspx). In the present study, Shuttle Radar Topographic Mission (SRTM) DEM of 30 m resolution was used for topographic analysis and geomorphic mapping of active tectonic features in the Piedmont alluvial plains. The DEM is available in geographic (lat/long) projection system with the WGS84 horizontal datum and the EGM96 vertical datum. The SRTM data is processed in Arc GIS (10.3) environment.
Change detection, risk assessment and mass balance of mobile dune fields near Dunhuang Oasis with optical imagery and global terrain datasets
Published in International Journal of Digital Earth, 2020
Chao Ding, Guangcai Feng, Mingsheng Liao, Lu Zhang
To better reveal the mass balance of sediment transport, two DEM datasets of Shuttle Radar Topography Mission (SRTM) X-band and TanDEM X-band both provided by the German Aerospace Center (DLR) are used here. The SRTM-X DEM was generated from Feb. 11 to 22, 2000 using radar interferometry technique, with a definition of around 25 m × 25 m (Ludwig and Schneider 2006). The horizontal and vertical accuracy is ±20 m (abs.) /± 15 m (rel.) and ±16 m (abs.) / ±6 m (rel.), respectively, both with 90% linear error. Due to the grid-like coverage limited by the narrow aperture angle, some data deficiency exists in this study area. Comparatively, TanDEM-X DEM were generated from 2010 to 2015 with absolute height error of ∼1 m, by two almost identical satellites flying in close orbits. Both the SRTM-X DEM and the product variant of TanDEM-X DEM with a reduced pixel spacing of 3 arc-seconds can be freely downloaded from https://download.geoservice.dlr.de/SRTM_XSAR/ and https://download.geoservice.dlr.de/TDM90/, respectively. The horizontal and vertical reference of these two different X-band DEM datasets are both the WGS84 datum with the EGM96 geoid as the vertical datum.