An assessment of independent component analysis for detection of military targets from hyperspectral images     

K.C. Tiwari  M.K. Arora  D. Singh 《International Journal of Applied Earth Observation and Geoinformation》2011

Hyperspectral data acquired over hundreds of narrow contiguous wavelength bands are extremely suitable for target detection due to their high spectral resolution. Though spectral response of every material is expected to be unique, but in practice, it exhibits variations, which is known as spectral variability. Most target detection algorithms depend on spectral modelling using a priori available target spectra In practice, target spectra is, however, seldom available a priori. Independent component analysis (ICA) is a new evolving technique that aims at finding out components which are statistically independent or as independent as possible. The technique therefore has the potential of being used for target detection applications. A assessment of target detection from hyperspectral images using ICA and other algorithms based on spectral modelling may be of immense interest, since ICA does not require a priori target information. The aim of this paper is, thus, to assess the potential of ICA based algorithm vis a vis other prevailing algorithms for military target detection. Four spectral matching algorithms namely Orthogonal Subspace Projection (OSP), Constrained Energy Minimisation (CEM), Spectral Angle Mapper (SAM) and Spectral Correlation Mapper (SCM), and four anomaly detection algorithms namely OSP anomaly detector (OSPAD), Reed–Xiaoli anomaly detector (RXD), Uniform Target Detector (UTD) and a combination of Reed–Xiaoli anomaly detector and Uniform Target Detector (RXD–UTD) were considered. The experiments were conducted using a set of synthetic and AVIRIS hyperspectral images containing aircrafts as military targets. A comparison of true positive and false positive rates of target detections obtained from ICA and other algorithms plotted on a receiver operating curves (ROC) space indicates the superior performance of the ICA over other algorithms.  相似文献   

Assessment of carbonaceous aerosol over Delhi in the Indo-Gangetic Basin: characterization, sources and temporal variability   总被引：1，自引：0，他引：1  

S. Tiwari  A. K. Srivastava  D. S. Bisht  P. D. Safai  P. Parmita 《Natural Hazards》2013,65(3):1745-1764

Semi-continuous measurements of organic carbon (OC) and elemental carbon (EC) and continuous measurements of black carbon (BC) and PM_2.5 aerosols were conducted simultaneously during the winter period of 2010–2011 at Delhi, one of the polluted urban megacities in western part of the Indo-Gangetic Basin region. The average mass concentrations of OC, EC, BC and PM_2.5 were about 54 ± 39, 10 ± 5, 12 ± 5 and 210 ± 146 μg m^?3, respectively. Contribution of total carbonaceous aerosol mass to PM_2.5 mass was found to be ~46 %. Average OC/EC ratio was found to be 5 ± 2 during the study period, suggesting the presence of secondary organic aerosols in the atmosphere over Delhi. Estimated mean secondary organic aerosol mass concentration was found to be 25 μg m^?3 and varied between 14.6 (February) and 37.0 μg m^?3 (December). A diurnal variation of OC and EC shows lower values during the day time and higher during the morning and night, which are highly associated with the corresponding variability in mixing layer heights. OC and EC were also found to be significantly correlated (r = 0.71) to each other, indicating their common sources. Concentrations of OC and EC were about 45 and 13 % higher during weekdays than weekends, respectively. Higher OC (67 %) and EC (53 %) were observed in the late evening during weekdays than those on weekends, which could be due to different emission sources during these two periods. The night/day ratio of EC and OC was found to be larger than 1.0, suggesting the relative accumulation of EC and OC near the surface at night hours.  相似文献   

Evaluation of hydrogeochemical processes and groundwater quality in the Jhansi district of Bundelkhand region, India   总被引：1，自引：0，他引：1  

Abhay Kumar Singh  Beenu Raj  Ashwani K. Tiwari  Mukesh K. Mahato 《Environmental Earth Sciences》2013,70(3):1225-1247

A base line study involving analysis of groundwater samples from the Jhansi district were carried out to determine the major and trace element chemistry and to assess the hydrogeochemical processes and water quality for domestic and irrigation uses. Study results show that groundwater is mildly acidic to alkaline in nature and HCO₃ ^?, Cl^?, Ca²⁺, Na⁺ and Mg²⁺ are the major contributing ions for the dissolved loads. The data plotted on the Gibbs and Piper diagrams reveal that the groundwater chemistry is mainly controlled by rock weathering with secondary contribution from anthropogenic sources. In a majority of the groundwater samples, alkaline earth metals exceed alkalies and weak acid dominate over strong acids. Ca–Mg–HCO₃ is the dominant hydrogeochemical facies in the majority of the groundwater samples. The computed saturation indices demonstrate that groundwater is oversaturated with respect to dolomite and calcite. Kaolinite is the possible mineral that is in equilibrium with the water, implying that the groundwater chemistry favors kaolinite formation. A comparison of groundwater quality parameters in relation to specified limits for drinking water shows that the concentrations of TDS, F^?, NO₃ ^?, total hardness and Fe are exceeding the desirable limits in many water samples. Quality assessment for irrigation uses reveal that the groundwater is of good to suitable category. Higher salinity and residual sodium carbonate values at some sites restrict the suitability of groundwater and need an adequate drainage and water management plan for the area.  相似文献   

Exploiting IKONOS and Hyperion data fusion for automated road extraction     

Poonam S. Tiwari  Hina Pande  Mya Nan Aye 《国际地球制图》2013,28(2):123-131

We present here the examples that show how fusing data from hyperspectral sensors with data from high spatial resolution sensors can enhance overall road detection accuracy. The fusion of hyperspectral and high spatial resolution data combines their superior respective spectral and spatial information. IKONOS (MSS) and Hyperion images were fused using the principal component analysis (PCA) method. The approach for road extraction integrates multiresolution segmentation and object oriented classification. Road extraction is done from an IKONOS (MSS) image and a Hyperion and IKONOS (MSS) merged image and comparisons are made depending on accuracy and quality measures such as completeness and correctness. This article also emphasises the types of roads which are giving better accuracy of extraction after fusion with hyperspectral image. This can vary because of types of material and condition of roads. The methodology was applied on roads of Dehradun, India.  相似文献   

Simulations of Tropical Circulation and Winter Precipitation Over North India: an Application of a Tropical Band Version of Regional Climate Model (RegT-Band)     

P. R. Tiwari  S. C. Kar  U. C. Mohanty  S. Dey  S. Kumari  P. Sinha  P. V. S. Raju  M. S. Shekhar 《Pure and Applied Geophysics》2016,173(2):657-674

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Effect of magnetic activity on ionospheric time delay at low latitude     

Soumi Bhattacharya  Smita Dubey  Rajesh Tiwari  P. K. Purohit  A. K. Gwal 《Journal of Astrophysics and Astronomy》2008,29(1-2):269-274

The purpose of this work is to investigate the effect of magnetic activity on ionospheric time delay at low latitude Station Bhopal (geom. lat. 23.2°N, geom. long. 77.6°E) using dual frequency (1575.42 and 1227.60 MHz) GPS measurements. Data from GSV4004A GPS Ionospheric Scintillation and TEC monitor (GISTM) have been chosen to study these effects. This paper presents the results of ionospheric time delay during quiet and disturbed days for the year 2005. Results show that maximum delay is observed during quiet days in equinoxial month while the delays of disturbed period are observed during the months of winter. We also study the ionospheric time delay during magnetic storm conditions for the same period. Results do not show any clear relationship either with the magnitude of the geomagnetic storm or with the main phase onset (MPO) of the storm. But most of the maximum ionospheric time delay variations are observed before the main phase onset (MPO) or sudden storm commencement (SSC) as compared to storm days.  相似文献   

Shear Driven Kinetic Alfven Wave with General Loss-Cone Distribution Function in the Plasma Sheet Boundary Layer     

B. V. Tiwari  Ruchi Mishra  P. Varma  M. S. Tiwari 《Earth, Moon, and Planets》2008,103(1-2):43-63

Expressions for the dispersion relation and growth rate of the KAW are derived for weak and strong shear regimes using the kinetic approach in view of the simultaneous observations of the large earthward Alfvenic Poynting flux, small-scale kinetic Alfven wave (KAW), earthward flowing electrons and upward flowing ions, at the substorm event in the plasma sheet boundary layer (PSBL). General loss-cone distribution function is adopted to describe the velocity distribution of the plasma particles. The results explain the generation of the observed KAW in the PSBL by the weak shear at the substorm onset. It is found that during the substorm expansion phase the cyclotron damping of KAW may lead to the upward flowing ion. Whereas, it’s Landau damping that may lead to the parallel energisation of the electrons that explains the observed loss of Alfvenic Poynting flux. It is also noted that the loss-cone distribution index changes the profiles of the frequency and growth rate plots of the shear-driven KAW. The loss-cone distribution function is therefore, an important factor for the excitation of KAW in the active region of the magnetosphere at the PSBL. Results are consistent with the finding of Wu and Seyler (J Geophys Res 108A6:1236, 2003) concerning kinetic Alfven wave generation and its stabilization by the sheared flow.  相似文献   

Application of the continuous wavelet transform of gravity and magnetic data to estimate sub‐basalt sediment thickness     

Palkesh Goyal  V.M. Tiwari 《Geophysical Prospecting》2014,62(1):148-157

The Continuous Wavelet Transform was recently proposed for the interpretation of gravity and magnetic potential data. We utilize the Continuous Wavelet Transform of gravity and magnetic data to address one of the most common issues in exploration geophysics: mapping of sub‐basaltic sedimentary strata. We observe that the magnetic response of the basaltic layer is dominant in a three‐layer case of a basalt‐sediment‐basement, whereas the gravity signal is dominated by the base of the sediment. Thus the Continuous Wavelet Transform of the magnetic data is related to the thickness of the basalt and the Continuous Wavelet Transform of the gravity data is related mostly to the bottom of the sediment. These observations are demonstrated with a synthetic model and a few field examples. Derived depths using Continuous Wavelet Transform are in good agreement with known vertical cross‐sections. Therefore, Continuous Wavelet Transform analysis of both gravity and magnetic data offers a possibility for primary information of sub‐basaltic sediment thickness, which can provide a basis for further detailed modelling.  相似文献   

Black carbon and chemical characteristics of PM<Subscript>10</Subscript> and PM<Subscript>2.5</Subscript> at an urban site of North India     

Suresh Tiwari  Atul K. Srivastava  Deewan S. Bisht  Tarannum Bano  Sachchidanand Singh  Sudhamayee Behura  Manoj K. Srivastava  D. M. Chate  B. Padmanabhamurty 《Journal of Atmospheric Chemistry》2009,62(3):193-209

The concentrations of PM₁₀, PM_2.5 and their water-soluble ionic species were determined for the samples collected during January to December, 2007 at New Delhi (28.63° N, 77.18° E), India. The annual mean PM₁₀ and PM_2.5 concentrations (± standard deviation) were about 219 (± 84) and 97 (±56) μgm⁻³ respectively, about twice the prescribed Indian National Ambient Air Quality Standards values. The monthly average ratio of PM_2.5/PM₁₀ varied between 0.18 (June) and 0.86 (February) with an annual mean of ∼0.48 (±0.2), suggesting the dominance of coarser in summer and fine size particles in winter. The difference between the concentrations of PM₁₀ and PM_2.5, is deemed as the contribution of the coarse fraction (PM_10−2.5). The analyzed coarse fractions mainly composed of secondary inorganic aerosols species (16.0 μgm⁻³, 13.07%), mineral matter (12.32 μgm⁻³, 10.06%) and salt particles (4.92 μgm⁻³, 4.02%). PM_2.5 are mainly made up of undetermined fractions (39.46 μgm⁻³, 40.9%), secondary inorganic aerosols (26.15 μgm⁻³, 27.1%), salt aerosols (22.48 μgm⁻³, 23.3%) and mineral matter (8.41 μgm⁻³, 8.7%). The black carbon aerosols concentrations measured at a nearby (∼300 m) location to aerosol sampling site, registered an annual mean of ∼14 (±12) μgm⁻³, which is significantly large compared to those observed at other locations in India. The source identifications are made for the ionic species in PM₁₀ and PM_2.5. The results are discussed by way of correlations and factor analyses. The significant correlations of Cl⁻, SO₄²⁻, K⁺, Na⁺, Ca²⁺, NO₃⁻ and Mg²⁺ with PM_2.5 on one hand and Mg²⁺ with PM₁₀ on the other suggest the dominance of anthropogenic and soil origin aerosols in Delhi.  相似文献   

Dynamic Analysis of Tunnel in Soil Subjected to Internal Blast Loading     

Rohit Tiwari  Tanusree Chakraborty  Vasant Matsagar 《Geotechnical and Geological Engineering》2017,35(4):1491-1512

The present work deals with the three-dimensional nonlinear finite element (FE) analyses of the tunnel in soil subjected to internal blast loading. The analyses are performed using the coupled Eulerian–Lagrangian analysis tool in FE software Abaqus/Explicit. The soil and reinforced concrete lining are modeled using the Lagrangian elements. The explosive Trinitrotoluene (TNT) is modeled using the Eulerian elements. The stress–strain response of soil, concrete, and reinforcement are simulated using strain rate dependent Drucker–Prager plasticity, concrete damaged plasticity and Johnson–Cook (J–C) plasticity models, respectively. The pressure–volume relationship of the TNT explosive is simulated using the Jones-Wilkins-Lee equation of state. Parametric sensitivity studies have been performed for different (1) tunnel lining thicknesses, (2) explosive charge weights and (3) angles of internal friction of soil. It is observed from the results that blast induced pressure on the tunnel lining increases with the increase in charge weight. Both the lining and the surrounding soil undergo significant deformation. The deformation of the tunnel lining increases with increasing charge weight and decreases with increasing lining thickness and increasing the angle of internal friction of soil. Blast-induced velocity in soil attenuates with increasing distance from the source of the blast.  相似文献