10 results on '"KRISHNAKUMAR, VRINDA"'
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2. Analysis of Deformation Dynamics in Guatemala City Metropolitan Area Using Persistent Scatterer Interferometry.
- Author
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García-Lanchares, Carlos, Marchamalo-Sacristán, Miguel, Fernández-Landa, Alfredo, Sancho, Candela, Krishnakumar, Vrinda, and Benito, Belén
- Subjects
METROPOLITAN areas ,NATURAL resources management ,INTERFEROMETRY ,EMERGENCY management ,URBAN planning ,SEISMOGRAMS ,SUSTAINABLE urban development - Abstract
The analysis of deformation dynamics in Guatemala city and its surrounding region presented in this paper holds significant relevance due to the high vulnerability of this area to natural disasters, combined with its rapid urbanization, similar to most Central American cities, contrasting with a lack of InSAR and deformation studies in the region. A total of 226 SAR images from Sentinel-1 A and B satellites in both ascending and descending geometries were processed with the Persistent Scatterer Interferometry (PSI) technique employing the SNAP-StaMPS integrated processing chain. The study area encompasses the Metropolitan Region of Guatemala, which is characterized by a diverse and active geological framework, with a historical record of earthquakes, intense groundwater extraction, and local subsidence phenomena, causing fissures and sinkholes. Four active areas were identified in the study area, each covering more than 50 hectares, with subsidence velocities greater than 10 mm/yr. This study provides valuable insights into fostering the sustainable development of this region by identifying deformation patterns, characterizing main active areas, and evaluating associated risks for disaster management and prevention. The results can also aid informed decision-making processes and guide urban planning and resource management strategies in other Central American countries. The application of InSAR studies is crucial for improving safety and sustainability in urban environments and natural resource management in vulnerable regions. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
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3. Sentinel-1 data exploitation for terrain deformation monitoring
- Author
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Krishnakumar, Vrinda, Universitat Politècnica de Catalunya. Departament de Física, and Monserrat, Oriol
- Subjects
Interferometry ,Sentinel-1 (artificial satellite) ,Enginyeria de la telecomunicació [Àrees temàtiques de la UPC] ,DInSAR ,Deformation - Abstract
Persistent Scatterer interferometry (PSI) is a group of advanced differential interferometric Synthetic Aperture Radar (SAR) techniques used to measure and monitor terrain deformation. Sentinel-1 has improved the data acquisition throughout and, compared to previous sensors, increased considerably the Differential Interferometric SAR (DInSAR) and PSI deformation monitoring potential. The effect of the refractive atmosphere on the interferometric phase and phase unwrapping ambiguity are two critical issues of InSAR. The low density of Persistent Scatterer (PS) in non-urban areas, another critical issue, has inspired the development of alternative approaches and refinement of the PS chains. Along with the efforts to develop methods to mitigate the three above-mentioned problems, the work presented in this thesis also deals with the presence of a new signal in multilooked interferograms which cannot be explained by noise, atmospheric or earth surface topography changes. This paper describes a method for atmospheric phase screen estimation using rain station weather data and three different data driven procedures to obtain terrain deformation maps. These approaches aim to exploit Sentinel-1 highly coherent interferograms and their short revisit time. The first method called the splitting makes uses of the power spectrum of the interferograms to split the signals into high and low frequency, and following a mutually exclusive consecutive processing chain for the two sets. This approach has resulted in greater density of PSs with decreased phase unwrapping errors. The second approach, called Direct Integration (DI), aims at providing a very fast and straightforward approach to screen wide areas and easily detect active areas. This approach fully exploits the coherent interferograms from the consecutive images provided by Sentinel-1 resulting in a very high sampling density. However, it lacks robustness and its usability lays on the operator experience. The third method, called PSIG (Persistent Scatterer Interferometry Geomatics) short temporal baseline, provides a constrained application of the PSIG chain, the CTTC approach to the PSI. It uses short temporal baseline interferograms and do not assume any deformation model for point selection. It is also quite a straightforward approach and a perfect complement to the direct integration approach. It improves the performances of the standard PSIG approach, increasing the PS density and providing robust measurements. The effectiveness of the approaches is illustrated through analyses performed on different test sites. La técnica Persistent Scatterer Interferometry (PSI) es un grupo de técnicas avanzadas de radar de apertura sintética interferométrica diferencial (SAR) que se utiliza para medir y monitorear losmovimientos del terreno. Sentinel-1 ha mejorado sensiblemente la adquisición de datos y, en comparación con los sensores SAR anteriores, ha aumentado considerablemente el potencial uso de la interferometría diferencial SAR y del PSI para medir y monitorizar desplazamientos del terreno. El efecto de la atmósfera sobre la fase interferométrica y la naturaleza ambigua de esta son dos cuestiones críticas de InSAR. Además, la baja densidad de Persistent Scatterer (PSs) en áreas no urbanas, es otro tema crítico que ha inspirado el desarrollo de enfoques alternativos y el refinamiento de las cadenas PS existentes. Junto con los esfuerzos por desarrollar métodos para mitigar los tres problemas antes mencionados, el trabajo presentado en esta tesis también aborda la presencia de una nueva señal en interferogramas multilooked que no puede explicarse por cambios de ruido, atmosféricos o topográficos de la superficie terrestre. Esta tesis describe un método para la estimación de la fase atmosférica utilizando datos meteorológicos adquiridos in-situ y tres aproximaciones diferentes basadas en datos Sentinel-1 para obtener mapas de deformación del terreno. Estos enfoques tienen como objetivo explotar los interferogramas altamente coherentes proporcionados por Sentinel-1 gracias a su corto tiempo de revisita. El primer método llamado división hace uso de filtros en el dominico frecuencial de los interferogramas para dividir las señales en alta y baja frecuencia, y siguiendo una cadena de procesamiento consecutiva independiente para cada clase. Este enfoque ha dado como resultado una mejora substancial de PS minimizando los errores debidos al desenrollado de fase. El segundo enfoque, llamado Integración Directa (DI), tiene como objetivo proporcionar un enfoque muy rápido y sencillo para examinar áreas amplias y detectar fácilmente áreas activas. Este enfoque aprovecha al máximo los interferogramas coherentes de las imágenes consecutivas proporcionadas por Sentinel-1, lo que da como resultado una densidad de muestreo muy alta. Sin embargo, carece de robustez y su usabilidad depende de la experiencia del operador. El tercer método, llamado PSIG (Persistent Scatterer Interferometry Geomatics) de línea de base temporal corta, proporciona una aplicación restringida de la cadena PSIG, el enfoque CTTC para el PSI. Utiliza interferogramas de línea base temporales cortos y no asume ningún modelo de deformación para la selección de puntos. Su uso es complementario al enfoque de integración directa proporcionando robustez en las zonas. Mejora el rendimiento del enfoque estándar de PSIG, aumentando la densidad de PS y proporcionando mediciones robustas. La efectividad de los enfoques se ilustra a través de análisis realizados en diferentes sitios de prueba.
- Published
- 2022
4. Classification of ground deformation using sentinel-1 persistent scatterer interferometry time series
- Author
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Mirmazloumi, S. Mohammad, primary, Wassie, Yismaw, additional, Navarro, José Antonio, additional, Palamà, Riccardo, additional, Krishnakumar, Vrinda, additional, Barra, Anna, additional, Cuevas-González, María, additional, Crosetto, Michele, additional, and Monserrat, Oriol, additional
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- 2022
- Full Text
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5. An innovative extraction methodology of active deformation areas based on sentinel-1 SAR dataset: the catalonia case study
- Author
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Qiu, Zhiwei, primary, Monserrat, Oriol, additional, Crosetto, Michele, additional, Krishnakumar, Vrinda, additional, and Zhou, Li, additional
- Published
- 2021
- Full Text
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6. Combining Satellite InSAR, Slope Units and Finite Element Modeling for Stability Analysis in Mining Waste Disposal Areas
- Author
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López-Vinielles, Juan, primary, Fernández-Merodo, José A., additional, Ezquerro, Pablo, additional, García-Davalillo, Juan C., additional, Sarro, Roberto, additional, Reyes-Carmona, Cristina, additional, Barra, Anna, additional, Navarro, José A., additional, Krishnakumar, Vrinda, additional, Alvioli, Massimiliano, additional, and Herrera, Gerardo, additional
- Published
- 2021
- Full Text
- View/download PDF
7. Sentinel-1 A-DInSAR Approaches to Map and Monitor Ground Displacements
- Author
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Krishnakumar, Vrinda, primary, Qiu, Zhiwei, additional, Monserrat, Oriol, additional, Barra, Anna, additional, López-Vinielles, Juan, additional, Reyes-Carmona, Cristina, additional, Gao, Qi, additional, Cuevas-González, Maria, additional, Palamà, Riccardo, additional, Crippa, Bruno, additional, and Gili, Jose Antonio, additional
- Published
- 2021
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8. Urban deformation monitoring using Sentinel-1 SAR data: a case study
- Author
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Crosetto, Michele, Monserrat, Oriol, Cuevas-González, Maria, Barra, Anna|||0000-0001-6254-7931, Krishnakumar, Vrinda, Crippa, Bruno, and Universitat Politècnica de Catalunya. Doctorat en Ciència i Tecnologia Aeroespacials
- Subjects
Interferometria ,Construction works ,monitoring ,Interferometry ,Enginyeria de la telecomunicació::Radiocomunicació i exploració electromagnètica::Teledetecció [Àrees temàtiques de la UPC] ,Monitoring ,construction works ,deformation ,interferometry ,Deformation ,SAR - Abstract
This paper describes the monitoring of the deformation associated to the construction works of a tunnel. The deformation is monitored using a Persistent Scatterer Interferometry technique and Sentinel-1 SAR data. A particular implementation of a PSI technique is described, which makes use of stable areas in the vicinity of the study area. The monitoring results include maps of accumulated deformation, to spatially describe the deformation, and deformation time series to describe the temporal evolution of deformation over the measured points., Grant numbers : the Catalan Government (2017-SGR-00729).
- Published
- 2019
- Full Text
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9. Comparison of Persistent Scatterer Interferometry and SAR Tomography Using Sentinel-1 in Urban Environment
- Author
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Budillon, Alessandra, primary, Crosetto, Michele, additional, Johnsy, Angel, additional, Monserrat, Oriol, additional, Krishnakumar, Vrinda, additional, and Schirinzi, Gilda, additional
- Published
- 2018
- Full Text
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10. ATMOSPHERIC PHASE DELAY IN SENTINEL SAR INTERFEROMETRY.
- Author
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Krishnakumar, Vrinda, Monserrat, Oriol, Crosetto, Michele, and Crippa, Bruno
- Subjects
ATMOSPHERIC waves ,SYNTHETIC aperture radar ,INTERFEROMETRY - Abstract
The repeat-pass Synthetic Aperture Radio Detection and Ranging (RADAR) Interferometry (InSAR) has been a widely used geodetic technique for observing the Earth's surface, especially for mapping the Earth's topography and deformations. However, InSAR measurements are prone to atmospheric errors. RADAR waves traverse the Earth's atmosphere twice and experience a delay due to atmospheric refraction. The two major layers of the atmosphere (troposphere and ionosphere) are mainly responsible for this delay in the propagating RADAR wave. Previous studies have shown that water vapour and clouds present in the troposphere and the Total Electron Content (TEC) of the ionosphere are responsible for the additional path delay in the RADAR wave. The tropospheric refractivity is mainly dependent on pressure, temperature and partial pressure of water vapour. The tropospheric refractivity leads to an increase in the observed range. These induced propagation delays affect the quality of phase measurement and introduce errors in the topography and deformation fields. The effect of this delay was studied on a differential interferogram (DInSAR). To calculate the amount of tropospheric delay occurred, the meteorological data collected from the Spanish Agencia Estatal de Meteorología (AEMET) and MODIS were used. The interferograms generated from Sentinel-1 carrying C-band Synthetic Aperture RADAR Single Look Complex (SLC) images acquired on the study area are used. The study area consists of different types of scatterers exhibiting different coherence. The existing Saastamoinen model was used to perform a quantitative evaluation of the phase changes caused by pressure, temperature and humidity of the troposphere during the study. Unless the phase values due to atmospheric disturbances are not corrected, it is difficult to obtain accurate measurements. Thus, the atmospheric error correction is essential for all practical applications of DInSAR to avoid inaccurate height and deformation measurements. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
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