Wavelet Based Post Classification Change Detection Technique for Urban Growth Monitoring     

R. A. Alagu Raja  V. Anand  A. Senthil Kumar  Sandeep Maithani  V. Abhai Kumar 《Journal of the Indian Society of Remote Sensing》2013,41(1):35-43

Urban areas are the most dynamic region on earth. Their size has been constantly increased during the past and this process will go on in the future. Since there is no standard policy and guidelines for construction of buildings and urban planning, cities tend to have irregular growth. Many cities in the world face the problem of urban sprawl in its suburbs. So issues of urban sprawl need to be settled with the help of technologies such as satellite remote sensing and automated change detection. This paper presents a wavelet based post classification change detection technique that is applied to 1996 and 2004 MSS images of Madurai City, South India to determine the urban growth. The classification stage of the technique uses coilflet wavelet filter to correlate with the MSS land cover images of Madurai city to derive texture feature vector and this feature vector is inputted to a fuzzy-c means classifier, an unsupervised classification procedure. The post classification change detection technique is employed for identifying the newly developed urban fringe of the study area. The error matrix analysis is used to assess the accuracy of the change map. The performance of the presented technique is found superior than that of classical change detection methods such as image differencing, change vector analysis and principal component analysis.  相似文献   

Geomorphic characterization of seafloor using Digital Elevation Model derivatives – a case study around Bombay High,Western Indian offshore     

Sandeep Narayan Kundu  Durga Shankar Pattnaik 《国际地球制图》2013,28(2):185-197

The present study demonstrates the use of gridded bathymetry in the form of a Digital Elevation Model (DEM) in a geographic information system (GIS) in geomorphic characterization of the seafloor in the Western Indian offshore around Bombay High region and presents the salient findings. The variography of bathymetry and its derivatives and their spatial correlation provides a technique to measure the presence of seafloor features and provides an insight into the processes involved. The current study utilizes tools available within a GIS for processing of a DEM and its derivatives involving spatial techniques like spatial correlation and variography studies for geomorphic characterization. A broad regional analysis for the study area comprising the near shore coast to the deep waters is discussed, followed up by a detailed study limiting to the coastal region around Bombay High.  相似文献   

美国俄亥俄州土壤有机碳密度空间分布(英文)   总被引：2，自引：1，他引：1  

Sandeep KUMAR  Rattan LAL  Desheng LIU  Rashid RAFIQ 《地理学报(英文版)》2013,23(2):280-296

Historical database of National Soil Survey Center containing 1424 geo-referenced soil profiles was used in this study for estimating the organic carbon(SOC) for the soils of Ohio,USA.Specific objective of the study was to estimate the spatial distribution of SOC density(C stock per unit area) to 1.0-m depth for soils of Ohio using geographically weighted regression(GWR),and compare the results with that obtained from multiple linear regression(MLR).About 80% of the analytical data were used for calibration and 20% for validation.A total of 20 variables including terrain attributes,climate data,bedrock geology,and land use data were used for mapping the SOC density.Results showed that the GWR provided better estimations with the lowest(3.81 kg m 2) root mean square error(RMSE) than MLR approach.Total estimated SOC pool for soils in Ohio ranged from 727 to 742 Tg.This study demonstrates that,the local spatial statistical technique,the GWR can perform better in capturing the spatial distribution of SOC across the study region as compared to other global spatial statistical techniques such as MLR.Thus,GWR enhances the accuracy for mapping SOC density.  相似文献   

Identification of landslide susceptible villages around Kalsubai region,Western Ghats of Maharashtra using geospatial techniques     

Praveen B. Gawali  Sainath P. Aher  B. V. Lakshmi  Ravindra D. Gaikwad  K. Deendayalan  Pramod T. Hanamgond  J. L. V. Mahesh Babu  Sandeep A. Arote  Shashikant I. Bairage 《Journal of the Geological Society of India》2017,90(3):301-311

Heavy rainfall triggered landslides are on the rise along the Western Ghats making it a matter of priority to identify landslide-prone areas well in advance. The present effort is aimed at identifying landslide susceptible villages (LSV) around the Kalsubai region of Deccan volcanic province (DVP), Maharashtra, India from 8 weighted landslide parameters- rainfall, slope, lithology, land use and land cover (LULC), soil properties, relative relief, aspect and lineament. These parameters were combined with advanced remote sensing (RS) data and processed in geographical information system (GIS) as well as in image processing software, which are an integral part of geospatial techniques. Out of the total 59 villages, the study identified 9 villages are situated in very high, 13 in high, 12 in moderate, 11 in low and 14 in very low risk zones. Our data reveals incessant heavy rains and steep slopes are the dominant factors in triggering landslides, exacerbated by anthropogenic activity prevalent in the study area. The spatial and non-spatial database created will help to take effective steps in preventing and/or mitigating landslide disasters in the study area. The methodology can be applied to identify other landslide prone areas in a cost effective way.  相似文献   

Geomorphological feature — A narrow rock bridge,Umthongkut area,West Khasi Hills district,Meghalaya     

S. K. Srivastava  P. K. Kothari  Sandeep Hamilton  Amit Majumdar 《Journal of the Geological Society of India》2009,74(2):284-284

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Himalayan Tectonics (The HIMPROBE Results)     

Sandeep Singh 《Gondwana Research》2004,7(2):635-636

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Viscous effects on penetrating shafts in clays     

Sandeep P. Mahajan  Muniram Budhu 《Acta Geotechnica》2006,1(3):157-165

The penetration of rigid objects such as piles and penetrometers into soils creates a zone of soil disturbance around them. The extent of this disturbed zone influences the resistance of the moving rigid body. This paper presents a theoretical framework to analyze the resistance in the disturbed zone created by a shaft penetrating a clay soil. The soil is modeled as a viscous material after it reaches failure [critical state (CS)]. The results of this analysis show that the viscous drag stress component on the shaft surface is influenced by the size of disturbed zone that has reached CS around the shaft, the shear viscosity of the soil and the velocity profile (or strain rate) in the CS zone around the shaft. The size of CS zone, the velocity profile and the viscosity of soil are interdependent. Large variation in viscous drag occurs when the size of the CS soil zone is less than four times the shaft’s radius. Limiting drag occurs when the size of the CS soil zone exceeds six times the shaft’s radius. The theoretical velocity distribution of the movement of soil in the CS zone shows that the soil is dragged along with shaft in the near field (close to the shaft surface) and moves upwards in the far field.  相似文献   

Impact of modification of initial cyclonic structure on the prediction of a cyclone over the Arabian Sea     

S. Sandeep  A. Chandrasekar  S. K. Dash 《Natural Hazards》2007,41(3):487-499

Most tropical cyclones have very few observations in their vicinity. Hence either they go undetected in standard analyses or are analyzed very poorly, with ill defined centres and locations. Such initial errors obviously have major impact on the forecast of cyclone tracks using numerical models. One way of overcoming the above difficulty is to remove the weak initial vortex and replace it with a synthetic vortex (with the correct size, intensity and location) in the initial analysis. The objective of this study is to investigate the impact of introducing NCAR–AFWA synthetic vortex scheme in the regional model MM5 on the simulation of a tropical cyclone formed over the Arabian Sea during November 2003. Two sets of numerical experiments are conducted in this study. While the first set utilizes the NCEP reanalysis as the initial and lateral boundary conditions, the second set utilizes the NCAR–AFWA synthetic vortex scheme. The results of the two sets of MM5 simulations are compared with one another as well as with the observations and the NCEP reanalysis. It is found that inclusion of the synthetic vortex has resulted in improvements in the simulation of wind asymmetries, warm temperature anomalies, stronger vertical velocity fields and consequently in the overall structure of the tropical cyclone. The time series of the minimum sea level pressure and maximum wind speed reveal that the model simulations are closer to observations when synthetic vortex was introduced in the model. The central minimum pressure reduces by 17 hPa while the maximum wind speed associated with the tropical cyclone enhances by 17 m s ⁻¹ with the introduction of the synthetic vortex. While the lowest central pressure estimated from the satellite image is 988 hPa, the corresponding value in the synthetic vortex simulated cyclone is 993 hPa. Improvements in the overall structure and initial location of the center of the system have contributed to considerable reduction in the vector track prediction errors ie. 642 km in 24 h, 788 km in 48 h and 1145 km in 72 h. Further, simulation with the synthetic vortex shows realistic spatial distribution of the precipitation associated with the tropical cyclone.  相似文献   

On the Prediction of Tropical Cyclones over the Indian Region Using a Synthetic Vortex Scheme in a Mesoscale Model     

S. Sandeep  A. Chandrasekar  S. K. Dash 《Pure and Applied Geophysics》2007,164(8-9):1443-1463

The tropical cyclones form over the oceanic regions where conventional meteorological observations are not available. This contributes to a poor initial analysis of the cyclonic vortex and hence inadequate forecast. One way of overcoming the above problem is to modify the initial analysis by replacing the weak and ill-defined vortex in the initial analysis with a synthetic vortex having the correct size and intensity at the correct location. In this study we are investigating the effect of inclusion of a synthetic vortex based on Rankine as well as on Holland wind profiles, using NCAR-AFWA bogussing scheme for the prediction of four tropical cyclones, which formed over the Bay of Bengal during November 2002 and 2005, December 2005 and over the Arabian Sea during May 2004, using the MM5 model. Two numerical experiments are designed in this study for each of the above four cyclones. In the first experiment the model is integrated with a synthetic vortex based on Rankine wind profile while in the second experiment we utilize the Holland wind profile. For the November 2002 cyclone, in both the experiments the model is integrated from 10 November 2002 18 UTC to 12 November, 2002 12 UTC with the synthetic vortex inserted at the initial time. The results of the study for the November 2002 cyclone show that the model simulation with the Holland vortex has produced a stronger cyclone in terms of minimum sea-level pressure and maximum wind speed. Also, the results for the November 2002 cyclone with the Holland vortex showed a better longitudinal height section of the horizontal wind speed across the center of the cyclone. The track error of the cyclone for the November 2002 cyclone is less in the model simulation with the Holland vortex at the initial time and at 24 hours of forecast. The results for the November 2002 cyclone with the Rankine vortex showed greater vertical wind speed as compared to the Holland vortex. However, for the November 2002 cyclone there were no significant differences in the spatial distribution of precipitation for both the experiments. In order to provide an adequate number of case studies for a good statistical sample, the present study is extended for three additional cyclones over the Indian region. All four cyclones studied here show that the Holland vortex has produced a stronger cyclone in terms of the minimum sea-level pressure and maximum wind speed. The Holland vortex showed a better vertical structure of wind speed in the longitudinal height section at 24 hours of forecast for the November 2005 cyclone while the structure was better for the Rankine vortex for the remaining two cyclones. There were no significant differences in the spatial distribution of precipitation for the two experiments corresponding to all four cyclones. Some statistical results pertaining to all four cyclones are provided such as the average track error as well as the average difference between the observed and the model minimum sea-level pressure and the maximum wind speed. The statistical results corresponding to the average of all the four cyclones are at only a slight variance with the results corresponding to the November 2002 cyclone.  相似文献   

Evaluation of physical and morphometric parameters for water resource management in Gad Watershed,Western Ghats,India: an integrated geoinformatics approach     

Sandeep Mahajan  R. Sivakumar 《Environmental Earth Sciences》2018,77(15):556

The selected study area is a coastal watershed which receives high rainfall in the monsoon season. During this period, most of the water input to the watershed drains to the Arabian Sea without any adequate use due to the rugged topography of the watershed. Hence, an attempt has been made to assess the physical properties specifically morphometric parameters of the Gad watershed using geoinformatics techniques along with field evidence for understanding the relationship between fluvial landforms and hydro-physical parameters in the region. Morphometric parameters have been analyzed and integrated with physical parameters like topography, rainfall, soil, land use–land cover, geology, and geomorphology for evaluating the potential water resource availability in the Gad watershed. The results of the study have shown that there is high surface water availability in the watershed with very low water retaining capacity, mainly in the upper region of the watershed due to presence of basaltic bedrock and steep slopes. Based on this work, a water resource management plan has been suggested at a subwatershed level which established on the physical properties and morphological characteristics of the study area.  相似文献