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Geodesy and Geodynamics 2022年第3期13卷 230-237页

作者： Gopal Sharma North Eastern Space Applications Centre Umiam793103MeghalayaIndia

Global Positioning System(GPS)Continuously Operating Reference Station(CORS)data analysis shows that the ionosphere’s electron density variability is linked to the deformation and stress accumulation in the Earth’s crust.Anomalies in ionosphere total electron content(TEC)variability before 2021 M6.4 Sonitpur,Assam earthquake were detected using L1 and L2 GPS frequencies that showed three distinct abnormalities on April 3,9,10,2021.Pearson’s correlation coefficient(r)of TEC decreases in the CORS that lies away from the earthquake epicenter,indicating the possibilities of a positive relationship between TEC variability and earthquake epicenter.TEC concentration also decreases towards the epicenter within the earthquake preparation zone(EPZ).It is also observed that the Pearson’s correlation coefficient(r)of TEC decreases linearly near the EPZ.The study demonstrates the possibilities of determining the TEC anomalous zone in the ionosphere that coincides with the EPZ in the crustal rocks.The research indicated the possibilities of magnitude estimation of an impending earthquake based on the TEC anomalous zone in the ionosphere using closely spaced dense CORS network data.

关键词： GPS TEC Sonitpur earthquake Ionosphere perturbation TEC anomaly Magnitude estimation

Quality assessment of Continuous Operating Reference Stations(CORS)-GPS stations in Mexico

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Geodesy and Geodynamics 2022年第3期13卷 275-287页

作者： Daniel Hernández-Andrade Rosendo Romero-Andrade Gopal Sharma Manuel E.Trejo-Soto Juan L.Cabanillas-Zavala Faculty of Earth and space Sciences Autonomous University of Sinaloa80013Culiacán RosalesSinaloaMexico North Eastern Space Applications Centre Umiam793103MeghalayaIndia

The present analysis provided the quality assessment of 65 Continuous Operating Reference Stations(CORS) situated in and around Mexico using the data of about ten years(January 2010 to January 2020).To accomplish the assessment,we considered 4 quality indexes for performing the quality check,incluing the multipath effect on L1 and L2 bands,signal-to-noise ratio in both bands,cycle slips,and integrity.Meanwhile,a new reference parameter named regio nal values for Mexico(RVM) was calculated for the stations situated in Mexico.Additionally,an exhaustive analysis of the quality indicators in the worst and best cases was performed.The signal degradation was proved by a long-term time series and cru stal defo rmation analysis in GAMIT/GLOBK platform.The results showed a stro ng correlation between integrity,cycle slips and daily observations time,and the multipath effect is strong in the case of outdated systems.The study indicates that the estimated quality indexes and values could be the basis for establishing new CORS in Mexico,and the errors corrections which cannot be mitigated in the postprocessing stage would greatly help utilize the data for different scientific applications.The results were supported by deformation analysis in part of Baja California Peninsula in Mexico indicating northern and eastern velocity vector of -3.08±0.02 mm/yr,-7.85±0.02 mm/yr and-0.07±0.03 mm/yr,-9.33±0.02 mm/yr respectively at MPR1 and INEG stations.

关键词： Multipath effect Signal-to-Noise ratio Cycle slip Integrity Regional quality indicators IGS indicators

Lightning Nowcasting with an Algorithm of Thunderstorm Tracking Based on Lightning Location Data over the Beijing Area

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Advances in Atmospheric Sciences 2022年第1期39卷 178-188页

作者： Abhay SRIVASTAVA Dongxia LIU Chen XU Shanfeng YUAN Dongfang WANG Ogunsua BABALOLA Zhuling SUN Zhixiong CHEN Hongbo ZHANG Key Laboratory of Middle Atmosphere and Global Environment Observation(LAGEO) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China space and Atmospheric Science Division North Eastern Space Applications CentreDepartment of SpaceMeghalaya 793103India

A thunderstorm tracking algorithm is proposed to nowcast the possibility of lightning activity over an area of concern by using the total lightning data and neighborhood technique.The lightning radiation sources observed from the Beijing Lightning Network(BLNET)were used to obtain information about the thunderstorm cells,which are significantly valuable in real-time.The boundaries of thunderstorm cells were obtained through the neighborhood technique.After smoothing,these boundaries were used to track the movement of thunderstorms and then extrapolated to nowcast the lightning approaching in an area of concern.The algorithm can deliver creditable results prior to a thunderstorm arriving at the area of concern,with accuracies of 63%,80%,and 91%for lead times of 30,15,and 5 minutes,respectively.The real-time observations of total lightning appear to be significant for thunderstorm tracking and lightning nowcasting,as total lightning tracking could help to fill the observational gaps in radar reflectivity due to the attenuation by hills or other obstacles.The lightning data used in the algorithm performs well in tracking the active thunderstorm cells associated with lightning activities.

关键词： neighborhood technique lightning nowcasting thunderstorm tracking lightning location data

Investigation on the COVID-19 Outbreak in India: Lockdown Impact and Vulnerability Analysis

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Journal of Geographic Information System 2020年第4期12卷 334-347页

作者： Nilay Nishant Avinash Chouhan Dibyajyoti Chutia Puyam S. Singh Sanjiv Ojah Sanjiban Roy P. L. N. Raju North Eastern Space Applications Centre Department of Space Umiam Meghalaya India

Coronavirus (COVID-19) disease is a major pandemic which has taken the world by storm. More than 524,000 citizens of the globe have succumbed to the disease as on 3rd July, 2020. Accurate modeling of the dynamics of the disease spread is required to curb the virus. With the availability of large amount of data made available publicly by the Government agency as well as the other live crowdsourcing media, it is possible to develop an accurate local prediction tool. In this study, we analyze the dynamics of local outbreaks of COVID-19 for few states of India with major outbreaks and for India as a whole. The large amount of data available from the COVID-19 Tracker India platform was utilized to estimate the impact of lockdown in the country and the states with major outbreaks. The effectiveness of the lockdown implementation by the respective states is studied for the analysis. The lockdown was categorized into strict, moderate, and lenient. The model is deployed on a web based platform to disseminate the alert to the public. We further extend the ordinary differential Equation (ODE) based model to generate district level vulnerability index for the whole country based on the rate of change of infected people, breach in social distancing, and population. Around 47% of districts of the country were not found vulnerable;however, 13% of the districts were identified as high risk for the disease outbreak.

关键词： COVID-19 Corona India Time Series Analysis SIR Model Vulnerability Analysis

A Geospatial Approach to Climatic Zone Specific Effective Horticultural Planning in East Khasi Hills District of Meghalaya, India

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Journal of Geographic Information System 2012年第3期4卷 267-272页

作者： Jonali Goswami Dibyajyoti Chutia S. Sudhakar Department of space North Eastern Space Applications Centre

Climatic zone is one of the most important units for horticultural planning. Survival and failure of particular land use or farming system in a given region heavily relies on careful assessment of agroclimatic resources. Large variety of crops is being grown in Meghalaya traditionally, based on the needs and cultural practices of people without any consideration to the suitability of the climate. This study attempts to make adjustments with the climate based upon scientific knowledge to make the best use of the natural resources so as to recommend more area under horticultural crops. This has been made by identifying existing land use and appropriate land use strategies mainly for horticultural crops for each agro-climatic region. Modern Geospatial technology such as satellite Remote Sensing (RS) and Geographical Information System (GIS) and GPS have been used effectively to provide newer dimensions in identifying suitable sites for various horticultural crops and also for appropriate monitoring and management of land resources in an integrated manner with reference to agro-climatic condition.

关键词： Climatic Zone Geospatial Technology RS GIS

Observed Relationship between Surface Freshwater Flux and Salinity in The north Indian Ocean

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Atmospheric and Oceanic Science Letters 2012年第3期5卷 163-169页

作者： Satya PRAKASH C. MAHESH Rakesh Mohan GAIROLA Atmospheric and Oceanic Sciences Group Space Applications Centre Indian Space Research Organisation

Using 10-year (2001 10) monthly evaporation, precipitation, and sea surface salinity (SSS) datasets, the relationship between local freshwater flux and SSS in the north Indian Ocean (NIO) is evaluated quantitatively. The results suggest a highly positive linear correlation between freshwater flux and SSS in the Arabian Sea (correlation coefficient, R=0.74) and the western equatorial Indian Ocean (R=0.73), whereas the linear relationships are relatively weaker in the Bay of Bengal (R=0.50) and the eastern equatorial Indian Ocean (R=0.40). Additionally, the interannual variations of freshwater flux and SSS and their mutual relationship are investigated in four sub- regions for pre-monsoon, monsoon, and post-monsoon seasons separately. The satellite retrievals of SSS from the Soil Moisture and Ocean Salinity (SMOS) and Aquarius missions can provide continuous and consistent SSS fields for a better understanding of its variability and the differences between the freshwater flux and SSS signals, which are commonly thought to be linearly related.

关键词：北印度洋水通量盐度表面线性关系卫星反演 SSS 中学校

A Novel Approach in Identification of Urban Hot Spot Using Geospatial Technology: A Case Study in Kamrup Metro District of Assam

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International Journal of Geosciences 2013年第5期4卷 898-903页

作者： Jonali Goswami Shreya Roy S. Sudhakar Department of space North Eastern Space Applications Centre Umiam India

Urbanization in recent years plays an important role in increase in impervious areas with reducing in vegetation cover and pervious areas of natural landscape. This leads to a rise in temperature of urban areas, by several degrees particularly at night [1,2]. A novel geospatial approach has been adopted to determine the maximum temperature areas (hot spots) over Kamrup Metro District of Assam, which is a gateway for seven neighboring north eastern states of India. The G statistics have been calculated for detecting the presence of hot spot or cold spot over the entire study area which is a new approach in urban heat island studies. The resultant z-scores and p-values show the pixels with either high or low values cluster spatially. For statistically significant positive z-scores, the larger the z-score is, the more intense the clustering of high values (hot spot) and vice versa. Land Surface Temperature (LST) anomaly values and percentage of Impervious Surface Area (ISA) along with climatic data are used to conform the hot spot location. It is one of the densely populated areas with more commercial pockets thereby giving rise to anthropogenic heat discharge which accelerates the heat island phenomenon. Incorporation of socio-economic survey data as well as certain biophysical parameters can be used to know about the cause and future impact of urbanization.

关键词： Hot Spot LST G Statistics Impervious Area Geospatial RS GIS

Development of a Web Based GIS Application for Spatial Natural Resources Information System Using Effective Open Source Software and Standards

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Journal of Geographic Information System 2012年第3期4卷 261-266页

作者： Puyam S. Singh Dibyajyoti Chutia Singuluri Sudhakar North Eastern Space Applications Centre Department of Space Govertment of India

There is growing needs for web based GIS for easy and fast dissemination, sharing, displaying and processing of spatial information which in turns helping in decision making for various natural resources based applications. In order to make a cost effective implementation, operation and maintenance of spatial information over the web, a cheaper yet feature rich alternative to commercial software is required which can be fulfilled by Open Source GIS software. This paper conveys an efficient approach to customize and integrate an open source web GIS system based on Mapserver as a web GIS server and PostgreSQL/PostGIS as an object oriented relational database management system (ORDBMS) for effective dissemination, sharing and management of spatial information over the internet. An open source web application tool built on top of MapScript using the PHP programming language has been used as for development of interactive user interface. The configurable Web Mapping Client Components (CWC2) tags have been added to HTML template pages in order to deploy the mapping contents to a web application. It is observed that the present system developed using open source software enables user to view, update, customized retrieval, query and analysis of natural resources information for specific needs.

关键词： GIS Mapserver ORDBMS CWC2 HTML

Effectiveness of Fuzzy Overlay Function for Multi-Criteria Spatial Modeling—A Case Study on Preparation of Land Resources Map for Mawsynram Block of East Khasi Hills District of Meghalaya, India

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Journal of Geographic Information System 2014年第6期6卷 605-612页

作者： Priyanka Baidya Dibyajyoti Chutia Singuluri Sudhakar Chandan Goswami Jonali Goswami Victor Saikhom Puyam S. Singh Kamini Kanta Sarma North Eastern Space Applications Centre Department of Space Government of India Umiam India

Multi-criteria spatial modeling is one of the important components of spatial decision support system (SDSS). Multi-criteria spatial modeling often requires a common scale of values for diverse and dissimilar inputs to create an integrated analysis. Weighted overlay function is most commonly used for site suitability analysis which identifies the most preferred locations for a specific phenomenon. However, weighted overlay function gives inconsistent and erroneous results for highly dissimilar inputs as it assumes that most favorable factors result in the higher values of raster, while identifying the best sites. This paper conveys the effectiveness of fuzzy overlay function for multi-criteria spatial modeling. It is based on the principle of fuzzy logic theory which defines membership using Gaussian function on each of the input rasters instead of giving individual rank to them like in weighted overlay function. A case study on preparation of land resources map for Mawsynram block of East Khasi Hills district of Meghalaya, India is presented here. It was observed that fuzzy overlay function has given more satisfactory output in terms of site suitability while comparing with the result of weighted overlay function.

关键词： Multi-Criteria Spatial Modeling Spatial Decision Support System (SDSS) Weighted Overlay Fuzzy Overlay

Land Suitability Analysis for Orange &Pineapple: A Multi Criteria Decision Making Approach Using Geo Spatial Technology

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Journal of Geographic Information System 2014年第1期6卷 40-44页

作者： Pratibha T. Das S. Sudhakar North Eastern Space Applications Centre Department of Space Government of India Umiam India

Land evaluation procedure given by FAO for soil site suitability for various land utilization types for rainfed agriculture has been used to assess the land suitability for khasi mandarin orange and pineapple in East Khasi Hills District of Meghalaya. The database on soil and land use/land cover was generated from IRS-P6 remote sensing satellite data, soil survey and laboratory analysis of soil samples to perform an integrated analysis in the Geographic Information System environment. Different soil chemical parameters and physical parameters were considered to evaluate soil site suitability for orange & pineapple. Different thematic layers were derived from soil map by using ArcGIS software. Subsequently all of them were overlaid and integrated in GIS environment and suitability criteria was applied to the resulted composite map and generated land suitability map for orange and pineapple. The result indicated that the soil sites of the study area are highly to marginally suitable for mandarin orange whereas it is marginally suitable for pineapple. The study reveals that highly suitable areas for orange are found in the Cherapunjee and Mawsynram area that covers 34.5 Sq.Km areas. Moderately suitable (37% of TGA) and marginally suitable (24% of TGA) areas are found only because of slope constraint (8%-30% slope). The hills with deep gorges and ravines on the southern portion of the district is found not suitable for orange plantation because of steep slopes (>30%) and stoniness. Land suitability analysis for pineapple showed that 81% area of total geographical area of the district is marginally suitable and 19% area is not suitable to support the crop. The district is marginally suitable because of topography (slope and erosion), soil fertility (base saturation and CEC) and climate.

关键词： Khasi Mandarin Orange Pineapple Site Suitability Analysis Soil Slope Remote Sensing GIS