Comparison of Different Mapping Techniques for Classifying Hyperspectral Data     

Vinay Kumar  R. D. Garg 《Journal of the Indian Society of Remote Sensing》2012,40(3):411-420

Hyperion is a space borne sensor which provides powerful tool in discriminating land cover features including urban area and in preparation of urban maps. It gives hyperspectral images in 242 bands within 400?nm to 2,500?nm wavelength range with 10?nm band-width. The Hyperion image in raw form is badly affected with several atmospheric effects which cause haziness. In this study hyperspectral image is atmospherically corrected by using FLAASH model of ENVI. After atmospheric correction the urban area was mapped using the spectral endmember collected by the procedure which includes minimum noise fraction (MNF), pixel purity index (PPI) and n-dimensional visualization in ENVI software. The aim of this study is to map the urban area using several mapping techniques such as Spectral Angle Mapper (SAM), Mixture Tune Matched Filtering (MTMF) and Linear Spectral Unmixing. The urban land covers displayed noticeable differences from one another in the spectral responses in the Hyperion image. The overall accuracy of the SAM classified map was 89.41%, which indicated good potential of Hyperion image for Classification. Use of the other approaches, linear spectral unmixing and MTMF have improved the classification results.  相似文献   

Role of the Water Vapour Greenhouse Effect in the Forecasting Of Fog Occurrence     

P. K. Pasricha  B. S. Gera  S. Shastri  H. K. Maini  T. John  A. B. Ghosh  M. K. Tiwari  S. C. Garg 《Boundary-Layer Meteorology》2003,107(2):469-482

Nocturnal measurements of air temperature, relative humidity, temperatureinversion-layer thickness, water vapour path and visibility-through-fog, madeunder non-foggy and foggy conditions in winter over two seasons at Delhi,are analysed to study the decrease in both rate of cooling and temperature inversion-layer thickness during the course of nights followed by fog occurrence.In particular, the decrease in the rate of cooling, compared to that on non-foggynights, is explained as due to the greenhouse warming effect by a layer of excessive,near-saturated water vapour trapped in a temperature inversion. Next, the linearprogramming technique is employed to forecast the occurrence of fog, where thevisibility-through-fog is minimized through its linear regression equation with thepair of variables, mean air temperature and temperature decrease over one hour(measuring rate of cooling at two convenient hours) in the pre-midnight period.This technique provides feasible solutions that enables one to forecast the occurrenceof radiative fog.  相似文献   

Spectral reflectance pattern study of some Indian landuse/landcover features     

K. P. Sharma  P. K. Garg  S. K. Verma 《Journal of the Indian Society of Remote Sensing》1986,14(1):11-16

To utilize the full potential of multispectral data acquired from aerial photographs/satellite imagery increased knowledge of the spectral reflectance characteristics of Landuse/Landcover features are required. Spectro-Radiometer was used to collect the spectral reflectance values in wavelength regions ranging from 0.48 to 0.96 u m, of some Landuse/Landcover features, in Roorkee and its surrounding areas. Spectral reflectance values, thus collected, were used to draw spectral reflectance curves of each feature separately and to determine the optimum wavelength regions for identifying each Landuse/Landcover feature. The wavelength regions, in which two dissimilar Landuse/Landcover features exhibit nearly same tonal variation in B&W aerial photographs/satellite imagery, were also determined from these curves.  相似文献   

Formation compaction associated with thermal cooling in geothermal reservoirs     

S. K. Garg 《Advances in water resources》1984,7(4):188-191

Concepts from the Theory of Interacting Continua are employed to develop constitutive relations for thermoelastic fluid-saturated porous media; these constitutive relations are shown to be equivalent to those of Biot in isothermal limit. For uniaxial compaction, the constitutive theory is simplified to give formation compaction as a function of changes in fluid pressure and temperature. The formation compaction due to thermal cooling is equal to 3hη[(1 + v)/3(1 − v)]ΔT.  相似文献   

On formation compaction and energy balance law for liquid-saturated porous media reservoirs     

S.K. Garg 《Advances in water resources》1985,8(1):22-25

In most treatments of liquid flow through porous media, it is assumed that the pore fluid and formation motions are decoupled except that porosity φ is taken to be a function of fluid pressure. This article examines the conditions under which such a decoupling is valid. More specifically, it is shown that the usual statements of the energy balance law ignore the work performed by the overburden as the formation compaction progresses. This work term is shown to be negligibly small in practical cases.  相似文献   

A comprehensive and quantitative assessment of Raunthi Gad flash flood,Rishi Ganga catchment,central Himalaya,Uttarakhand, India     

Nainwal  Harish Chandra  Shankar  R.  Mishra  Aditya  Mishra  Sumit  Pandey  Ankit  Shah  Sunil Singh  Chauhan  Gambhir Singh  Kumar  Deepak 《Natural Hazards》2022,113(1):157-184

Natural Hazards - Drought severity is increasing in Southern Africa which is affecting rain-fed agriculture, the main source of livelihood in most countries in this region. The study assessed the...  相似文献   

Groundwater prospects evaluation based on hydrogeomorphological mapping using high resolution satellite images: A case study in Uttarakhand     

Md. Surabuddin Mondal  A. C. Pandey  R. D. Garg 《Journal of the Indian Society of Remote Sensing》2008,36(1):69-76

Water is the most important natural resource which forms the core of the ecological system. The advent of remote sensing has opened up new vistas in groundwater prospect evaluation, exploration and management. The groundwater resources of the study area, Rishikesh region of Garhwal Himalayas, are under threat due to population pressure caused by expanding tourism in this region. This entails sustainable and judicious use of this precious resource. The groundwater prospect evaluation in Rishikesh region has been attempted based on hydrogeomorphological mapping of the area consisting of thematic maps of hydrogeomorphology, geology, drainage, lineament, slope and relief using high resolution IRS-1C LISS III and PAN merged satellite images. The Rishikesh region exhibits diverse hydrogeomorphological conditions where the groundwater regime is controlled mainly by topography and geology. A probability-weighted approach has been applied during overlay analysis in ArcMap GIS environment. The overlay analysis allows a linear combination of weights of each thematic map with respect to ground water potential. Good groundwater prospects dominate in the area with more than 50% of the study area showing moderate to excellent potential. The study shows that the remote sensing and geoinformatics techniques can be applied effectively for groundwater prospect evaluation.  相似文献   

Effect of photoelectric emission on blunt probe conductivity measurements in the stratosphere     

Thomas John  P. Chopra  S.C. Garg 《Journal of Atmospheric and Solar》2009,71(8-9):905-910

Two identical planar blunt probes of stainless steel material, biased with a bipolar ramp voltage, are used to measure the stratospheric polar conductivities to altitudes of 34 km. One probe (DP) is mounted closer to the gondola, looking downwards and shielded from sunlight, while the other (SP) is mounted looking sideways, away from the gondola. The daytime observations of positive ions in the 29–34 km altitude range with SP, and of negative ions at 34 km with DP, show photoelectric contaminations induced by solar UV radiations in the 190–230 nm band. These contaminations are found to be due to photoemissions from the SP probe steel surface and from the carbon paint that coats the surface of the gondola, respectively. It is found that, a segment of the photocurrent contaminated I–V curve, recorded with SP at higher negative probe potentials, is linear, and it can give the ambient positive polar conductivity.  相似文献   

Design of a High Efficiency Acoustic Phased Array Antenna for an Acoustic Wind Profiler     

R. M. Khanna  O. Sharma  S. C. Garg 《Meteorology and Atmospheric Physics》1999,71(1-2):35-41

Summary Improvements to the performance of acoustic wind profilers necessitate designing efficient acoustic antennas for the profilers, so that weak echoes can be received to enhance data availability. An efficient acoustic antenna needs to optimize electrical to acoustic and acoustic to electrical conversion efficiency as measured at the antenna axis. It also needs to provide a good directional response, and be able to handle increased electrical power. Phased array antennas, designed using piezo-electric transducers, should provide better characteristics in this regard. In the present study several different transducer elements were characterized with respect to their relative efficiencies. On the basis of this characterization, measurement of acoustic background noise at the expected site of antenna location and comparative study of atmospheric molecular absorption at the element peak efficiency frequencies, it is concluded that Motorola KSN 1025 A transducer is the best speaker element for the array antennas for profilers up to around 500 meters. The present array antenna has been designed using 104 KSN 1025 A piezo-electric transducer elements. The corner elements were removed from a 16 × 8 element speaker matrix, yielding an irregular octagonal pattern. Before installing the elements in the array, each element was individually characterized for its transmit and receive conversion efficiency, and variations in the product of these efficiencies (conversion gain) amongst the different elements, has been usefully employed to taper the array gain from centre to periphery. The antenna was systematically characterized, in an acoustic anechoic chamber, with respect to its axial transmit and receive conversion efficiencies and directional response. Received October 14, 1998 Revised March 1, 1999  相似文献   

Application of Four Measurement Techniques to Understand Natural Source Zone Depletion Processes at an LNAPL Site     

Poonam R. Kulkarni  Charles J. Newell  David C. King  Lisa J. Molofsky  Sanjay Garg 《Ground Water Monitoring & Remediation》2020,40(3):75-88

There are several key data gaps in our understanding of Natural Source Zone Depletion (NSZD) processes at sites impacted by light nonaqueous phase liquid (LNAPL), and quantifying NSZD rates can be challenging due to the inherent differences in measurement methods. In this study, four different NSZD measurement methods (oxygen influx measured by the Gradient Method, long-term carbon dioxide efflux measured with Carbon Traps, instantaneous carbon dioxide efflux measured with Dynamic Closed Chambers (DCC LI-COR), and the long-term heat flux from biodegradation measured by Thermal NSZD monitoring), as well as LNAPL composition and dissolved gas sampling, were applied at a site in Southern California. These techniques were used to evaluate key questions such as: (1) how do different NSZD rate measurement methods compare, and what causes variability in NSZD results?; (2) to what extent NSZD processes are occurring in LNAPL within the saturated zone?; and (3) how is NSZD related to LNAPL composition change over time? Carbon Traps and Thermal NSZD monitoring measurement methods provided the most consistent NSZD data at this geologically heterogeneous site, with two location average NSZD rates of 540 and 480 gal/acre/year, respectively. Overall, comparisons of NSZD rates between methods were challenging due to different measurement timeframes, significant temporal and spatial heterogeneity, and operational challenges with two of the NSZD methods. Finally, samples of subsurface LNAPL were collected for analysis in 2007 and 2016; results indicated that diesel-range constituents were already very degraded and anaerobic degradation of gasoline-range constituents was ongoing. A LNAPL depletion model (Douglas et al. 1996) applied to the measured LNAPL composition change appeared to greatly overestimate the amount of LNAPL depletion compared to the measured NSZD rate, but did provide an independent semiqualitative line of evidence that LNAPL was being depleted by active NSZD processes at the site.  相似文献