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Geoscience and Remote Sensing Symposium, 1994. IGARSS '94. Surface and Atmospheric Remote Sensing: Technologies, Data Analysis and Interpretation., International

Date 8-12 Aug 1994

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Displaying Results 1 - 25 of 197
  • Tikhonov's method of the ground-based radiometric retrieval of the ozone profile

    Publication Year: 1994 , Page(s): 1901 - 1903 vol.4
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    The incorrect problem of the ozone height profile retrieval by ground-based measurements of the brightness temperatures in ozone spectral lines has been considered elsewhere only by using recurrence numerical methods based on properly chosen height discretization. Such an approach is mathematically inconsistent and does not allow the true retrieval possibilities to be established. The method based on the Tikhonov's theory has been worked out in order to solve the problem and numerical simulation in the lines centred at 110.8 and 142.2 GHz. The influence of measurement errors, spectral band width, and channel number in the spectral band on the retrieval of the ozone profile peculiarities at different height levels is investigated View full abstract»

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  • The generation and propagation of internal wave forms in the Strait of Gibraltar studied by ERS-1 SAR imagery and a numerical model

    Publication Year: 1994 , Page(s): 2023 - 2025 vol.4
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    The generation and propagation of internal waves in the Strait of Gibraltar has been studied by analyzing 131 ERS-1 SAR scenes from 78 satellite overflights over this area in the period from December 1991 to February 1994. From the analysis of the ERS-1 SAR images the authors obtain the following results: (1) roughness patterns over the Camarinal Sill are visible from 1h after low tide at Gibraltar until 6h after low tide, (2) sea surface manifestations of eastward propagating internal waves are observed at distances from 23 km to 160 km from the Camarinal Sill, (3) the mean propagation speed of these internal waves is 2.0 ms -1, and (4) the spatial separation between the first two internal waves in a wave train ranges from 1.1 km inside the strait to 10 km in the Alboran Sea. The roughness pattern inside the strait are explained by a one-dimensional numerical model based on the Boussinesq equations for two water layers of different densities. The non-hydrostatic primitive shallow water equations include horizontal diffusion, bottom and interfacial friction. The model allows mean flows in both layers and is driven by a tidal flow at the open boundary. The proposed model explains the observed temporal and spatial evolution of roughness patterns inside the Strait of Gibraltar as well as the east-west asymmetry of the internal wave field View full abstract»

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  • Application of multilayer feedforward neural networks to precipitation cell-top altitude estimation

    Publication Year: 1994 , Page(s): 1870 - 1872 vol.4
    Cited by:  Papers (3)
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    The use of passive 118-GHz O2 observations of rain cells for precipitation cell-top altitude estimation is demonstrated using a multilayer feedforward neural network retrieval system. Data was derived from a collection of 118-GHz rain cell observations along with estimates of the cell-top altitude obtained by optical stereoscopy. The observations were made using the millimeter wave temperature sounder (MTS) scanning spectrometer aboard the NASA ER-2 research aircraft during the Genesis of Atlantic Lows Experiment (GALE) and the Cooperative Huntsville Meteorological Experiment (COHMEX), 1986. The neural network estimator applied to MTS spectral differences between clouds and nearby clear air yielded an RMS discrepancy of 1.77 km for a combined cumulus, mature and dissipating cell set and 1.50 km for the cumulus-only set. A slight improvement in RMS discrepancy to 1.48 km was achieved by including additional MTS information on the absolute atmospheric temperature profile. Comparison of these results with a nonlinear statistical estimator shows that superior results can be obtained with the neural network retrieval system. The neural network estimator was then used to create imagery of cell-top altitudes estimated from 118-GHz CAMEX spectral imagery gathered from September through October, 1993 View full abstract»

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  • Small slope approximation for microwave polarimetric observation of the sea surface

    Publication Year: 1994 , Page(s): 2421 - 2423 vol.4
    Cited by:  Papers (3)
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    The thermal microwave emission of the sea surface is determined mainly by the resonant ripples at near-nadir angles of observation (Irisov et al., 1987). Their amplitudes and directions of propagation are closely related to the local wind speed and direction. The anisotropy of the surface gravitational-capillary waves leads to a polarization dependence, which can be used for the remote sensing of the near-surface wind. The small-slope approximation is developed to calculate the brightness temperature of the rough ocean surface, taking into account the whole sea spectrum. The estimation of the higher order terms is made. The possibility of scanning for full polarization measurements is considered View full abstract»

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  • An inverse technique for obtaining cirrus cloud microphysical parameters using combined radar and lidar backscatter measurements

    Publication Year: 1994 , Page(s): 1904 - 1906 vol.4
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    A technique utilizing NOAA's ground-based infrared lidar and millimeter radar measurements to infer range-resolved cirrus cloud microphysical parameters is presented. An example of cloud properties retrieved from lidar and radar backscatter data obtained during a recent cloud field experiment is shown to illustrate this retrieval technique View full abstract»

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  • ERS-1 SAR images of atmospheric gravity waves

    Publication Year: 1994 , Page(s): 2026 - 2028 vol.4
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    ERS-1 synthetic aperture radar (SAR) images of atmospheric gravity waves are discussed. One case study is presented in detail, in which it is shown that the intense long wavelength phenomenon observed in the SAR image is an atmospheric gravity wave generated by the passage of a warm front. Atmospheric soundings and a 2-layer model indicate that the wave phenomenon could have been supported by the observed temperature inversion layer and accompanying wind shear View full abstract»

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  • Simulation of a polarimetric random noise/spread spectrum radar for subsurface probing applications

    Publication Year: 1994 , Page(s): 2494 - 2498 vol.4
    Cited by:  Papers (2)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    A novel polarimetric ultra-wideband radar system operating in the 1-2 GHz frequency range for subsurface probing applications is currently under development at the University of Nebraska. Spread spectrum and random noise signals are being explored as possible modulation waveforms. Detection and localization of buried objects is accomplished by correlating the reflected waveform with a time-delayed replica of the transmitted waveform. Broadband dual-polarized log-periodic antennas are used for transmission and reception. A unique signal processing scheme is used to obtain the target's polarimetric amplitude and phase response by frequency translation of the ultra-wideband signal by a coherent 160 MHz phase-locked source. In addition, the radar system features high depth resolution, low bandwidth-duration product, as well as simplified signal processing. In this paper, the results of computer simulations of the radar system performance covering a wide range of modulation waveforms, soil moisture conditions, depth/orientation/type of buried objects are described and compared. The simulation studies confirm the ability of the proposed radar system to image and identify various types of buried objects View full abstract»

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  • Development of a high resolution ice echo sounder for Arctic ice sheet

    Publication Year: 1994 , Page(s): 2401 - 2402 vol.4
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    An ice core experiment conducted jointly by Japan and Canada was initiated in the Arctic region three years ago. It is now planned to drill the ice cap in the Canadian Arctic which would yield ice samples that have been in existence for hundreds of years. To start this study, ion concentrations, micro particles chemistry and the electrical properties of the ice and melt water having been measured to reconstruct paleoclimate/environment in the Arctic region. In order to support this program, a new type of echo sounder has been developed by Communications Research Laboratory (CRL). It has a capability of detecting the structure of ice beneath a surface with high resolution View full abstract»

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  • Simulation study of a microwave radiometric temperature profiler for the Antarctic atmosphere

    Publication Year: 1994 , Page(s): 2436 - 2438 vol.4
    Cited by:  Papers (2)
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    Describes a simulation study carried out by applying the radiative transfer equation to a data base of radiosoundings released from the Dumont d'Urville station, located in the proximity of the Eastern coasts of Antarctica. This study was conducted for defining the specifications of the radiometric channels and for assessing an inversion algorithm for temperature profile retrieval, suitable for the foreseen operational mode of a continuously working ground based microwave radiometer observing the Antarctic atmosphere View full abstract»

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  • Design of a Ka band polarimetric radiometer

    Publication Year: 1994 , Page(s): 2419 - 2420 vol.4
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    In order to develop the capability of conducting more efficient research flights, the University of Massachusetts secured funding from the U.S. Navy to develop a Ka band polarimetric radiometer for future airborne surveys. The design, which is discussed, uses concepts developed as part of the ESTAR thinned array radiometer project, which uses correlation techniques to image terrain at L-Band. This paper discusses the design of the authors' polarimeter and the development status. The authors also discuss other potential applications other than the measurement of wind direction View full abstract»

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  • Coastline detection from SAR images

    Publication Year: 1994 , Page(s): 2134 - 2136 vol.4
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    Coastline detection from synthetic aperture radar (SAR) images is in the category of edge or boundary detection. But the lack of contrast between the ocean and nearby land areas makes the ordinary edge detection methods inferior. Ocean areas in SAR images, however, are much more homogeneous in grey levels than land areas and features reflecting the “roughness” of an image can be very useful for sea-land separation. This paper tests several features. Experiment results show that the best result is given by the absolute deviation from the mean extracted using a 7×7 scanning window and that a reasonable sea-land separation can be obtained from it with the help of Gibbs distribution. But misclassification occurs if a land area is homogeneous enough or a sea area is also “rough”. This is manifested in the segmentation image as surplus small “lakes” and “islands” which are eliminated if their area is below the user-specified threshold. Another problem is the blurring effect of the window operation. The consequence is found to be an over-segmentation of the land areas and so deblurring is done through an even contraction of the land areas. The detected coastlines are found, when overlaid on the original image, to coincide quite well with the true situation View full abstract»

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  • Stereo passive remote sensing of aerosol transport and diffusion

    Publication Year: 1994 , Page(s): 1907 - 1910 vol.4
    Cited by:  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    Atmospheric aerosol transport and diffusion in the planetary boundary layer is characterized by high spatial and temporal variability. Point and single line of sight sensors provide insufficient information necessary for detailed evaluation of aerosol transport and diffusion models, for detecting the trajectory of hazardous material releases, or measurement of environmental pollution. A stereo passive remote sensing system providing detailed smoke screen transport and diffusion measurements during U.S. Army field tests offers extensive aerosol transport and diffusion measurement capability. The system uses digital image processing of thermal image data to provide a pixel by pixel two-dimensional map (perpendicular to the observers line of sight) of transmission or path integrated concentration. The ambient (natural) background scene in the imager field of view is the radiometric source against which transmission measurements are made. Additionally, the system uses sets of multispectral imagers in stereo pairs to obtain generalized three dimensional descriptions of smoke screen transport and diffusion. These data are used to compute the path taken by the centroid of the smoke screen and overall cloud dimensions as a function of time. Time resolution for the system is 10 Hz. The ability of the system to provide three dimensional aerosol transport and diffusion data and path integrated aerosol concentration maps with sufficient sensitivity to evaluate transport and diffusion models in detail, and to detect hazardous material trajectories and environmental pollution is demonstrated analytically and experimentally View full abstract»

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  • Field-of-view calibration of the Microwave Limb Sounder on the Upper Atmosphere Research Satellite

    Publication Year: 1994 , Page(s): 2224 - 2227 vol.4
    Cited by:  Papers (1)
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    Describes the field-of-view (FOV) calibration of the Microwave Limb Sounder (MLS) on board NASA's Upper Atmosphere Research Satellite (UARS). Calibration data are derived from measurements and analytical models, combined with in flight data. Particular emphasis is given to pointing calibration and estimation of far sidelobe levels and radiance offsets, using both the Moon and the residual signals when the FOV is pointed high above Earth's atmosphere View full abstract»

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  • On-line complex permittivity measurements for ground penetrating radar

    Publication Year: 1994 , Page(s): 2513 - 2515 vol.4
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    One of the major problems for a subsurface radar to predict is the true target distance and maximum likely penetration depth in the media under investigation. These radar parameters can be determined from the complex permittivity of the media. Since the permittivity of the surface under examination is usually unknown, most subsurface radars are calibrated in time units only: actual subsurface distances have to be inferred from other knowledge of the soil/rock. This paper presents a technique to provide on-line, complex permittivity measurements for the ground penetrating radar, to help predict these important distance parameters. The system consists of an electrically short monopole antenna backed by a ground plane; the input impedance of the antenna is a function of the complex permittivity of the surrounding media. Using a model for the complex input impedance of the antenna, the electrical properties of the media can be determined. To test the performance of the system, measurements were taken to determine the electrical properties of air, salt water and pure water, since these properties are known accurately via Debye's formula. Measurements of the complex permittivity of sand as a function of frequency and water content, as well as the permittivity of the saline solutions are presented. This system was then integrated into a stepped frequency continuous wave ground penetrating radar. Tests using targets buried at known depths in a large sand box were used to verify the performance of the system and its limitations. Results of field trials are presented View full abstract»

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  • Performance verification of spectral and panchromatic modules of the MOMS-02 sensor flown aboard STS-55/D2-mission

    Publication Year: 1994 , Page(s): 2301 - 2304 vol.4
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    A second generation instrument of the MOMS (Modular Optoelectronic Multispectral/Stereo Scanner) was flown in the frame of the German D2 mission aboard Space Shuttle flight STS-55. The newly designed sensor provides multispectral coverage in 4 bands including the visible and near-infrared range. In addition, MOMS-02 is equipped with a three line along track stereo device recording for/aft and nadir panchromatic data. During the mission (April to May 1993) approximately 7 mio. km2 of data have been recorded in 7 different modes from a mean altitude of 296 km resulting in a GIFOV of 4.5×4.5 m2 in the nadir panchromatic and 13.5×13.5 m2 in the panchromatic for/aft and multispectral bands. MOMS-02 data of distinct test-sites, recorded at different conditions have been investigated on its quantitative and qualitative performance. Different algorithms are used for estimating entropy, signal to noise ratio, point spread function and interband correlation. The results are related to complementary LANDSAT TM and SPOT HRV data sets. The first impression of the raw data was quite positive as compared to the data of the pilot system MOMS-01. Recognizable image distortions could be related to electronic malfunctions and/or to lack of power, shielding and thermal (heating-up) influences. These problems are identified and will he solved for future missions by change of electronic parts and supply of a sufficient thermal environment. The entropy, SNR and PSF performances an comparable to the operational sensors. However, MOMS band 3 is slightly weaker in its performance especially in the SNR. The reason for this was found in electronic malfunctions and may also be related to the band width design that is about 10 nm narrower than the nominal (originally defined) one. Results of the correlation analysis confirm the new arrangement of the band centers and widths. An improvement in spectral dynamic of about 10-15% versus a broad banded design could be estimated View full abstract»

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  • The impact of the ocean wave-radar modulation transfer function on the inversion of ERS-1 SAR image spectra into ocean wave spectra

    Publication Year: 1994 , Page(s): 2032 - 2034 vol.4
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    Hasselmann's closed forward integral transform and its inversion includes, in addition to motion induced effects, the modulation of the normalized radar cross section (NRCS) due to long ocean waves. This modulation is described by a linear ocean wave-radar modulation transfer function (MTF). The authors compute the forward mapping integral by using a `theoretical' and a parameterized form of the MTF with variable moduli and phases. For range propagating waves the transformation of SAR image spectra into ocean wave spectra depends strongly on this MTF. Significant wave heights (Hs) derived from inverted wave spectra decrease by 15-20% when increasing the modulus of the MTF by a factor of 2. Furthermore, Hs increases up to 50% if a phase of 0° is used in the forward mapping integral instead of the most likely phase of the MTF which is 90 View full abstract»

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  • Active microwave measurements of snow cover progress in polarimetric SAR

    Publication Year: 1994 , Page(s): 1922 - 1924 vol.4
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    In hydrological investigations, modeling and forecasting of snow melt runoff requires information about snowpack properties and their spatial variability. In particular, timely measurement of snow parameters is needed for operational hydrology. This paper reports the authors' recent progress on deriving snow covered area and snow wetness by using the NASA/JPL airborne and SIR-C/X-SAR spaceborne polarimetric synthetic aperture radar (SAR) imagery. Mapping areas covered by wet snow in remote alpine regions by using single polarization SAR imagery requires topographic information to obtain correct radiometric measurements and to reduce angular dependence for discrimination. However, the mapping of wet snow by using measurements of the polarization properties from the polarimetric SAR does not require topographic information. The authors have developed and tested an algorithm for snow wetness retrieval using C-band polarimetric SAR imagery. Test results using JPL AIRSAR and SIR-C data show that the authors' algorithms can be used to provide quantitative estimates of liquid water content in the top layer of a snowpack View full abstract»

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  • A comparison of simulation techniques for correlated gamma and K-distributed images for SAR applications

    Publication Year: 1994 , Page(s): 2182 - 2184 vol.4
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    Discusses clutter simulation which is an important element in the development of target detection algorithms for radar remote sensing. SAR images are well represented by the K distribution and an important feature of SAR clutter is the autocorrelation function. Methods are described for the generation of realisations from a correlated K distribution with specified correlation properties. Higher order correlations are also considered View full abstract»

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  • Comparison and visualization of feature space behaviour of statistical and neural classifiers of satellite imagery

    Publication Year: 1994 , Page(s): 1880 - 1882 vol.4
    Cited by:  Papers (1)
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    Currently both statistical and neural classifiers are being used for the classification of multispectral satellite imagery. Because both classifier types are being used as `black boxes' and because they are values based on different mathematical models the reasons for their different performance levels are not well understood. The authors have used visualization of class decision boundaries in feature space as a means to gain insight into the classification processes View full abstract»

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  • Multispectral LANDSAT images segmentation using neural networks and multi-experts approach

    Publication Year: 1994 , Page(s): 2109 - 2111 vol.4
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    The application of a combined segmentation method using the Canny-Deriche filter and a multi layer perceptron neural network is considered. The segmentation of five LANDSAT spectral bands is conducted. Obtained segmented images are combined using a multi experts approach in order to improve the segmentation quality and to preserve the land cover regions View full abstract»

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  • A study on whole three years data analysis of NOAA AVHRR images

    Publication Year: 1994 , Page(s): 2541 - 2543 vol.4
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    As a fundamental study of the image database category index, the authors have been analysing the classification of sea and land levels based on the albedo value obtained from NOAA-11 satellite at the area of northern Japan. The target image is NOAA AVHRR CH2 image, which has been studied automatic data analysis of the whole set of data for a period of three years (1990.4~1993.3). The authors tried to relate the sea and land level by albedo value with the elevation of Sun when the satellite observed. The classification method is unique technique because of matching the CH2 image with sea and land data, whose data is composed of 0 and 1 values. The authors have shown the change of albedo of the image category corresponding to the seasonal change. Also shown is the classification of sea and land levels (the tangent of time and elevation of Sun) are rising year by year. The authors have proposed the recognition ratio of sea and land as a new key word of NOAA AVHRR CH2 image search index View full abstract»

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  • Cross-section estimation by simulated annealing

    Publication Year: 1994 , Page(s): 2188 - 2190 vol.4
    Cited by:  Papers (2)
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    Presents an algorithm which performs radar cross-section estimation by using techniques based on simulated annealing. Standard simulated annealing approaches to image restoration attempt to categorise each image element as belonging to one of a small number of predefined image states or values. This is restrictive for tasks such as radar cross-section estimation and the authors present an algorithm which is capable of producing a real-valued output. This is achieved by introducing an edge detection stage into the simulated annealing process. The action of the annealing algorithm may be viewed as a filter which adapts to local image structure. The authors present results which demonstrate this behaviour and in so doing allow them to estimate the residual noise levels that might be expected View full abstract»

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  • Analysing spatio-temporal characteristics of surface parameters from NOAA AVHRR data

    Publication Year: 1994 , Page(s): 2097 - 2100 vol.4
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    Knowledge on the spatio-temporal variability of surface parameters such as surface temperature, albedo or percentage vegetation cover is an important prerequisite for environmental modeling on regional to global scales. Data of this kind are generally lacking. However, they may be derived from remote sensing data with appropriate spatial and temporal resolutions. Given the regional to global extension of model calculations and considering the surface parameters of interest, the AVHRR on board the NOAA satellites currently is the only sensor capable of providing the required information. The paper describes the use of geostatistical methods for the analysis of multitemporal sets of surface parameters as derived from AVHRR data. Through the retrieval of semi-variograms for varying grid-cell sizes and directions, the spatial variability of the given surface parameters is described. By fitting models to the experimental semi-variograms, parameters such as the range and the sill may be retrieved in an consistent, reliable and automatic way. While the systematic analysis of images allows for the description of the spatial distribution of these parameters, the analysis of multitemporal data sets results in the description of their temporal evolution. The paper presents the methodology and results obtained for a multi-year set of HRPT data. It shows the difference in scale, strength, and cyclic behaviour of the spatial variability to be expected from different surface parameters View full abstract»

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  • Transmitted radiation of searchlight in turbid atmosphere

    Publication Year: 1994 , Page(s): 1911 - 1913 vol.4
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    It is shown how to get an analytically Cauchy system of the scattering and transmission functions in the searchlight problem in a turbid atmosphere bounded by a diffuse reflector. An invariant imbedding leads to an initial-value solution of the scattering and transmission functions for the searchlight. The Riccati-type of nonlinear integro-differential equations are used. The authors discuss the convergence of the solutions. An approximate solution is found in terms of the standard scattering and transmission functions in a turbid slab of the same optical thickness. Finally, it is shown how to compute numerically such three-dimensional, nonlinear integro-differential equations with the aid of an asymptotic operator method and the Monte Carlo method View full abstract»

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  • NOAA AVHRR data processing: requirements and limitations in operational algorithms

    Publication Year: 1994 , Page(s): 2519 - 2521 vol.4
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    NOAA AVHRR data are now widely used in many applications, where the required precision is clearly higher than the required by the original meteorological applications. Three main steps can be considered in the development of a data processing scheme for AVHRR data: radiometric calibration, geometric processing and reflectance/temperature retrieval through atmospheric/radiometric corrections, including also cloud screening and the elaboration of a database to work with temporal series of data through multitemporal composites. A complete AVHRR data processing algorithm is presented. Some considerations about data processing techniques to meet the precision requirements of advanced applications, in which quantitative analysis require accurate and validated data, are also discussed View full abstract»

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