A Comparative Investigation of Image Fusion in the Context of Classification     

Anshu Gupta  Vivek Dey 《Journal of the Indian Society of Remote Sensing》2012,40(2):167-178

Image fusion assists in visual interpretation, mapping, change detection and many other applications. Multispectral and Panchromatic images are fused to produce images having enhanced spatial and spectral properties. These properties are generally distorted from original images. The aim of this paper is to identify the effectiveness of the several fusion techniques based on the distortions and applications. This paper employs seven image fusion techniques namely, Brovey transform, intensity hue saturation, high pass filter, principle component analysis, UNB Pansharpening, wavelet transform and multiplicative, available in various commercial image processing software. The data for this study are panchromatic image of Cartosat-1 and multispectral image of IRS - P6 LISS 4 sensor of study area, Bhopal Municipal Corporation area, M.P. State, India. The effectiveness of image fusion techniques is determined by quantitative and qualitative assessments. Quantitative assessment is divided into two parts: 1) assessment of fusion techniques by statistical parameters and 2) accuracy assessment of land use maps generated from the fused images. For part 1, three parameters namely, mean bias, correlation coefficient and Q4 quality index, have been used. Based on the results of part 1, UNB Pansharpening and wavelet transform are the best among seven fusion techniques. For part 2, Gaussian and Artificial Neural Network classifiers have been used to generate land cover maps. However, the accuracy results are inconclusive to identify a single best method. Nevertheless, image fusion by wavelet transform has provided best results in both the sector. Hence, wavelet transform is concluded as the best among selected fusion techniques.  相似文献   

Aquifer Sensitivity to Pesticide Leaching: Testing a Soils and Hydrogeologic Index Method     

Edward Mehnert  Donald A. Keefer  William S. Dey  H. Allen Wehrmann  Steven D. Wilson  Chittaranjan Ray 《Ground Water Monitoring & Remediation》2005,25(4):60-67

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Torsional surface wave in an elastic half-space with void pores     

S. Dey  S. Gupta  A. K. Gupta 《国际地质力学数值与分析法杂志》1993,17(3):197-204

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Geology,geomorphology and mineral resources of khodana and adjoining areas (Haryana) and their significance in landuse planning     

R. C. Dey 《Journal of the Indian Society of Remote Sensing》1985,13(1):57-68

The area around Khodana, Bhiwani district, Haryana forms a part of the semi-arid region of western India. As vegetation is sparse and mainly xerophytic, photointerpretation technology was effectively utilised in bringing out the broad geology and structural pattern of the mature Precambrian terrain, which were ground-checked and correlated with the results of detailed integrated surveys carried out for base metal sulphide mineralisation in the area. A number of shear/fault zones, sub-parallel to the formational contacts and the regional fold axes, could be recognised in aerial photographs and on ground checking, were found to be intensely limonitised. The possibility of direct application of the pyrite-pyrthotite, encountered in drilling through shear zones, in landuse planning has been discussed. Discrete use of the quartzites as road ballasts, building stone and bund material, use of clay-rich pockets within pasture lands or micro-depressions in the surrounding terrain for locally-constructed brick kilns and ochreous material as pigments are some other uses of finite land resources of Haryana State.  相似文献   

Time series effects of dissolved oxygen and nitrogen on Long Island Sound lobster harvest     

Zinnia Mukherjee  Dipak K. Dey  Rangan Gupta 《Natural Hazards》2016,84(3):1849-1858

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Distribution of suspended sediment concentration in wide sediment‐laden streams: A novel power‐law theory          下载免费PDF全文

Francisco Nicolás Cantero‐Chinchilla  Oscar Castro‐Orgaz  Subhasish Dey 《Sedimentology》2016,63(6):1620-1633

The diffusion equation of suspended sediment concentration in a wide sediment‐laden stream flow is dependent on the vertical gradient of streamwise velocity and the sediment diffusivity. This study aims at investigating the influence of the streamwise velocity laws on the suspended sediment concentration distributions, resulting from the solution of the diffusion equation. Firstly, the sediment concentration distributions are obtained numerically from the solution of the diffusion equation using different velocity laws and compared with the experimental data. It is found that the power‐law approximation produces good computational results for the concentration distributions. The accuracy of using a power‐law velocity model is comparable with the results obtained from other classical velocity laws, namely log‐law, log wake‐law and stratified log‐law. Secondly, a novel analytical solution is proposed for the determination of sediment concentration distribution, where a power‐law, wall‐concentration profile is coupled with a concentration wake function. The power‐law model (for velocity and concentration) is calibrated using the experimental data, and then a generalized wake function is obtained by choosing a suitable law. The developed power‐law model involving the wake function adjusted by an exponent predicts the sediment concentration distributions quite satisfactorily. Finally, a new explicit formula for the suspended‐load transport rate is derived from the proposed theory, where numerical computation of integrals, as needed in the Einstein theory, is avoided.  相似文献   

Old high-redshift galaxies and primordial density fluctuation spectra     

Peacock  Jimenez  Dunlop  Waddington  Spinrad  Stern  Dey  & Windhorst 《Monthly notices of the Royal Astronomical Society》1998,296(4):1089-1097

We have discovered a population of extremely red galaxies at z  ≃ 1.5 which have apparent stellar ages of ≳ 3 Gyr, based on detailed spectroscopy in the rest-frame ultraviolet. In order for galaxies to have existed at the high collapse redshifts indicated by these ages, there must be a minimum level of power in the density fluctuation spectrum on galaxy scales. This paper compares the required power with that inferred from other high-redshift populations: damped Lyα absorbers and Lyman-limit galaxies at z  ≃ 3.2. If the collapse redshifts for the old red galaxies are in the range z _c ≃ 6–8, there is general agreement between the various tracers on the required inhomogeneity on 1-Mpc scales. This level of small-scale power requires the Lyman-limit galaxies to be approximately ν ≃ 3.0 fluctuations, implying a very large bias parameter b  ≃ 6. If the collapse redshifts of the red galaxies are indeed in the range z _c = 6–8 required for power spectrum consistency, their implied ages at z  ≃ 1.5 are between 3 and 3.8 Gyr for essentially any model universe of current age 14 Gyr. The age of these objects as deduced from gravitational collapse thus provides independent support for the ages estimated from their stellar populations. Such early-forming galaxies are rare, and their contribution to the cosmological stellar density is consistent with an extrapolation to higher redshifts of the star formation rate measured at z  < 5; there is no evidence for a general era of spheroid formation at extreme redshifts.  相似文献   

An approach of understanding acid volcanics and tuffaceous volcaniclastics from field studies: A case from Tadpatri Formation,Proterozoic Cuddapah basin,Andhra Pradesh,India     

Sukanta Goswami  P K Upadhyay  Sangeeta Bhagat  Syed Zakaulla  A K Bhatt  V Natarajan  Sukanta Dey 《Journal of Earth System Science》2018,127(2):20

The lower stratigraphic part of the Cuddapah basin is marked by mafic and felsic volcanism. Tadpatri Formation consists of a greater variety of rock types due to bimodal volcanism in the upper part. Presence of bimodal volcanism is an indication of continental rift setting. Various genetic processes involved in the formation of such volcanic sequence result in original textures which are classified into volcaniclastic and coherent categories. Detailed and systematic field works in Tadpatri–Tonduru transect of SW Cuddapah basin have provided information on the physical processes producing this diversity of rock types. Felsic volcanism is manifested here with features as finger print of past rhyolite-dacite eruptions. Acid volcanics, tuffs and associated shale of Tadpatri Formation are studied and mapped in the field. With supporting subordinate studies on geochemistry, mineralogy and petrogenesis of the volcanics to validate field features accurately, it is understood that volcanism was associated with rifting and shallow marine environmental condition. Four facies (i.e., surge, flow, fall and resedimented volcaniclastic) are demarcated to describe stratigraphic units and volcanic history of the mapped area. The present contribution focuses on the fundamental characterization and categorization of field-based features diagnostic of silica-rich volcanic activities in the Tadpatri Formation.  相似文献   

Estimating threshold-exceeding probability maps of environmental variables with Markov chain random fields   总被引：2，自引：2，他引：0  

Weidong Li  Chuanrong Zhang  Dipak K. Dey  Shanqin Wang 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(8):1113-1126

Estimating and mapping spatial uncertainty of environmental variables is crucial for environmental evaluation and decision making. For a continuous spatial variable, estimation of spatial uncertainty may be conducted in the form of estimating the probability of (not) exceeding a threshold value. In this paper, we introduced a Markov chain geostatistical approach for estimating threshold-exceeding probabilities. The differences of this approach compared to the conventional indicator approach lie with its nonlinear estimators—Markov chain random field models and its incorporation of interclass dependencies through transiograms. We estimated threshold-exceeding probability maps of clay layer thickness through simulation (i.e., using a number of realizations simulated by Markov chain sequential simulation) and interpolation (i.e., direct conditional probability estimation using only the indicator values of sample data), respectively. To evaluate the approach, we also estimated those probability maps using sequential indicator simulation and indicator kriging interpolation. Our results show that (i) the Markov chain approach provides an effective alternative for spatial uncertainty assessment of environmental spatial variables and the probability maps from this approach are more reasonable than those from conventional indicator geostatistics, and (ii) the probability maps estimated through sequential simulation are more realistic than those through interpolation because the latter display some uneven transitions caused by spatial structures of the sample data.  相似文献   

Understanding mass fluvial erosion along a bank profile: using PEEP technology for quantifying retreat lengths and identifying event timing          下载免费PDF全文

A. N. Thanos Papanicolaou  Christopher G. Wilson  Achilles G. Tsakiris  Tommy E. Sutarto  Fabienne Bertrand  Massimo Rinaldi  Subhasish Dey  Eddy Langendoen 《地球表面变化过程与地形》2017,42(11):1717-1732

This study provides fundamental examination of mass fluvial erosion along a stream bank by identifying event timing, quantifying retreat lengths, and providing ranges of incipient shear stress for hydraulically driven erosion. Mass fluvial erosion is defined here as the detachment of thin soil layers or conglomerates from the bank face under higher hydraulic shear stresses relative to surface fluvial erosion, or the entrainment of individual grains or aggregates under lower hydraulic shear stresses. We explore the relationship between the two regimes in a representative, US Midwestern stream with semi‐cohesive bank soils, namely Clear Creek, IA. Photo‐Electronic Erosion Pins (PEEPs) provide, for the first time, in situ measurements of mass fluvial erosion retreat lengths during a season. The PEEPs were installed at identical locations where surface fluvial erosion measurements exist for identifying the transition point between the two regimes. This transition is postulated to occur when the applied shear stress surpasses a second threshold, namely the critical shear stress for mass fluvial erosion. We hypothesize that the regimes are intricately related and surface fluvial erosion can facilitate mass fluvial erosion. Selective entrainment of unbound/exposed, mostly silt‐sized particles at low shear stresses over sand‐sized sediment can armor the bank surface, limiting the removal of the underlying soil. The armoring here is enhanced by cementation from the presence of optimal levels of sand and clay. Select studies show that fluvial erosion strength can increase several‐fold when appropriate amounts of sand and clay are mixed and cement together. Hence, soil layers or conglomerates are entrained with higher flows. The critical shear stress for mass fluvial erosion was found to be an order of magnitude higher than that of surface fluvial erosion, and proceeded with higher (approximately 2–4 times) erodibility. The results were well represented by a mechanistic detachment model that captures the two regimes. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献