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Geoscience and Remote Sensing, IEEE Transactions on

Issue 1 • Date Jan. 1987

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Displaying Results 1 - 24 of 24
  • IEEE Transactions on Geoscience and Remote Sensing

    Page(s): c1
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  • IEEE Geoscience and Remote Sensing Society

    Page(s): c2
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  • Table of contents

    Page(s): 1
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  • Systematic Ground-Based Measurements of Mesospherc Water Vapor and Radio Wave Absorption

    Page(s): 2 - 6
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    Ground-based microwave radiometry has been used to remotely measure mesospheric water vapor during the late winter and spring of 1983-1984 and through the winter of 1984 and spring of 1985. The 22.235-GHz spectral emission line has been observed with a cryogenically cooled MASER low-noise receiver. A simple measure of the emission feature is obtained by fitting a best fit exponential to each spectra. During the same time interval, an "A3" radio wave absorption experiment monitored D-region ionospheric radio absorption. A comparison is made of the observed water vapor spectral height and area to the observed radio wave absorption. During active sun conditions (1983-1984) radio wave absorption seems uncorrelated to the water vapor. However, during quiet sun conditions, some general agreement between the spectral area and radio wave absorption is observed. Long term variations of 2 to 1 in the water vapor spectral height are found. View full abstract»

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  • A New Inversion Technique for Apparent Resistivity Measurements

    Page(s): 7 - 10
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    A new algorithm for interpreting apparent earth resistivity data obtained from depth sounding measurements is presented. The method is based on fitting the data to an N layer earth model with equal layer heights h where h is equal to the required depth resolution. The spectral reflection coefficient at the earth's surface for the model used is derived as a ratio of two polynomials, the coefficients of which are a function of the resistivity ratios of adjacent layers. This provides the theoretical basis for inferring the model parameters. Measures for improving numerical stability are suggested and applied to a few examples. Results show that the present algorithm is most suited for continuously varying resistivity depth profiles. View full abstract»

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  • Development of Signal Processing Methods for Imaging Buned Pipes

    Page(s): 11 - 15
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    A new imaging technique for subsurface radars is described for reconstructing clear images of buried pipes in soil. The method developed has two signal processing stages; preprocessing and aperture synthesis. The preprocessing extracts signals scattered from the pipes by reducing clutter noise. The synthetic-aperture processing analyzes only the scattered signals derived by the first stage and reconstructs high-quality images in a short processing time. The imaging technique developed was successfully applied to the imaging of actual buried metallic pipes. It was experimentally confirmed that the new imaging method was capable of reconstructing clear images in a short time without losing image quality. View full abstract»

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  • A New Microwave Radiometer Simultaneously Receiving Dual-Polarized Radiation

    Page(s): 16 - 21
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    A new cost-effective microwave radiometer has been designed for simultaneously receiving both vertically and horizontally polarized thermal radiation, which are important signals for improving the capability of passive remote observations of geophysical phenomena. It is basically a Dicke-switched superheterodyne receiver whose both polarization channels share a single set of a reference noise source, a low-noise microwave amplifier, and a mixer with a local oscillator by adopting a scheme that both channels are slightly spaced in receiving frequency. A 15-GHz band radiometer has been built and tested for the verification of this scheme. View full abstract»

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  • How Wind Affects Passive Microwave Measurements of Sea Surface Temperature

    Page(s): 22 - 27
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    Uncertainty in the wind speed is a major source of error in passive microwave measurements from satellites of sea surface temperature (SST) because of the non-linear relationship between sea surface emissivity and wind speed. The accuracy of the SST measurement that can be achieved with only passive microwave measurements was assessed by computer modeling. Our investigation showed that the second-order terms must be included in the equation of radiative transfer in an analysis of the errors in the retrieved SST. In addition, we found that the effects of wind roughening and foam production should be treated separately. We have concluded that the accuracy of SST measurements would be improved by including data from an active remote-sensing instrument such as a scatterometer. View full abstract»

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  • Autonomous Extraction of an Eddy-Like Structure from Infrared Images of the Ocean

    Page(s): 28 - 34
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    The amount of imagery generated by all the various satellite-borne thermal infrared sensors is great and constantly growing. To analyze this imagery manually is tedious and time consuming. The present paper is concerned with automating the extraction of one important, though often weak, type of oceanic feature viz. isolated blob structure. These "blobs" usually correspond to distinct oceanographic features such as eddies or regions of upwelling. The technique proposed to achieve this aim is based on finding the structural relationship between connected regions of constant grey level (i.e., constant temperature). These elementary connected regions are known as atoms. The relationship between atoms is described by a region adjacency graph with the position on the graph being determined by the depth of enclosure of the particular atom. An eddy-like structure is extracted by searching the graph for isolated atoms of high temperature that are enclosed by atoms of lower temperatures (for warm core eddies). Techniques of preprocessing to reduce the search problem to managable proportions and methods to deal with cloud and land "contamination" are also described. The examples given are based on thermal imagery from the Heat Capacity Mapping Mission (HCMM). View full abstract»

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  • Nimbus 7 SMMR Investigation of Snowpack Properties in the Northern Great Plains for the Winter of 1978-1979

    Page(s): 35 - 46
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    An investigation of the capabilities of remote sensing of snowpack properties was conducted with brightness temperatures from the Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) and climatological data for the northern Great Plains for the winter of 1978-1979. The radiometer data included horizontally and vertically polarized brightness temperatures at the 0.81-, 1.66-, and 2.80-, and 4.54-cm wavelengths for both day and night overpasses, with a repeat coverage on the average of every two to three days. The brightness temperatures in each channel and the daily surface climatological elements of maximum and minimum air temperature, precipitation, snowfall, and snow depth were objectively analyzed to a 20-km grid with 35 rows and 42 columns. The analysis concentrated on temporal analyses of selected grid cells. Characteristic signatures were observed for initial snow accumulation, snow depth to about 20 cm, beginning of snow melting in the surface layers, and snow melt. The process of snow ripening was evident in the thawing and refreezing cycles of the snow surface layers. Discrimination of dry soil, wet soil, snow amount to 15 cm, and liquid water at the soil surface before runoff occurred was present with the use of both polarizations at the 0.81- and 1.66-cm wavelengths, although the longer wavelengths contained additional information on the state of the surface underlying the snow pack. View full abstract»

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  • Calculations of the Microwave Brightness Temperature of Rough Soil Surfaces: Bare Field

    Page(s): 47 - 54
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    A model for simulating the remotely sensed microwave brightness temperatures of soils with rough surfaces is developed. The surface emissivity of the soil media is calculated from one minus its reflectivity, which is obtained by the integration of the bistatic scattering coefficients for rough soil surfaces. The soil brightness temperature is obtained from the product of the surface emissivity and the effective soil temperature, which is calculated with measured soil moisture profiles and soil temperature profiles at various soil depths. The roughness of a soil surface is characterized by two parameters, the surface height standard deviation a and its horizontal correlation length l. The model calculations are compared to the measured angular variations of the polarized brightness temperatures at both L-band (1.4 GHz) and C-band (5 GHz) frequencies. A nonlinear least squares fitting method is used to match the model calculations with the data, and the best fit results produce the parameter values of a and l that best characterize the surface roughness. The effect of rough surface shadowing is also incorporated into the model by introducing a shadowing function S(¿), which represents the probability that a point on a rough surface is not shadowed by other parts of the surface. The model results for horizontal polarization are in excellent agreement with the data, both qualitatively and quantitatively. For vertical polarization, some discrepancies exist between the calculations and data. Possible causes of the discrepancy are discussed. View full abstract»

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  • Shuttle Imaging Radar (SIR-B) Investigations of the Canadian Shield: Initial Report

    Page(s): 55 - 66
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    Two of the 43 Shuttle Imaging Radar (SIR-B) experiments carried out from the 41-G shuttle mission in 1984 involved a 2600-km swath across the Canadian Shield, with the objectives of studying the structure of province boundaries and developing techniques for the geologic use of orbital radar. Despite degraded single incidence angle imagery resulting from system problems, valuable experience has been obtained with data over a test site near Bancroft, Ontario. It has been found that even subdued glaciated topography can be effectively imaged, variations in backscatter being caused by variations in local incidence angle rather than shadowing. It has been demonstrated that small incidence angles are more sensitive to topography than large angles. Backscatter is extremely sensitive to look direction, topographic features nearly normal to the illumination being highlighted, and those nearly parallel to it being suppressed. It is concluded that orbital radar can provide a valuable tool for geologic studies of the Canadian Shield and similar areas, if suitable look angles and at least two look directions can be utilized for each area. View full abstract»

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  • Multipolarization SAR Data for Surface Feature Delineation and Forest Vegetation Characterization

    Page(s): 67 - 76
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    This paper presents the utility of multipolarization Synthetic Aperture Radar (SAR) data for surface feature delineation and forest vegetation characterization. Three channels of ratioed data (VV/HH, VH/HH, and VH/VV) are generated from the HH, VV, and VH polarization data (V = vertical, H = horizontal). The ratioed data are linearly stretched to yield a digital number within a range of 0 to 255. The techniques for reducing SAR speckle noise and for measuring the degree of separation are discussed. For surface feature delineation, the results indicate that cross polarization as well as cross polarization ratioed data better delineate those surface features that are difficult to separate by like polarization data. The results suggest using a median value filtering technique to reduce within-plot data fluctuation to increase the separability measure. For forest vegetation characterization, the results indicate that multipolarization SAR data may be used to estimate forest properties such as total-tree biomass, basal area, and tree height. View full abstract»

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  • Interpretation of the Polarimetric Co-Polarization Phase Tern in Radar Images Obtained with the JPL Airborne L-Band SAR System

    Page(s): 77 - 82
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    The utilization of both polarimetric amplitude and relative phase terms of the polarization scattering matrix [S] given for each pixel, is pursued for polarimetric SAR imagery interpretation. The existing amplitude-only backscattering approaches hitherto used are extended and modified to accommodate the interpretation of information contained in the amplitude and/or phase terms. Both a vector radiative transfer model for surface versus volume scattering from rough terrain with and without vegetation canopy and a high-frequency electrical curvature model for perfectly conducting surfaces are examined to come up with theoretical models that out-perform other hitherto known approaches. The developed models agree with the excellent polarimetric SAR imagery recently obtained with the JPL CV-990 dual-polarization L-band (1.225 GHz) SAR system. Recommendations are made on how to further perfect the system for integration in the SIR-C and other future polarimetric SIR-SAR systems. View full abstract»

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  • Relating Polaization Phase Difference of SAR Signals to Scene Properties

    Page(s): 83 - 92
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    This paper examines the statistical behavior of the phase difference AO between the HH-polarized and VV-polarized backscattered signals recorded by an L-band SAR over an agricultural test site in Illinois. Polarization-phase difference (¿¿) distributions were generated for about 200 agricultural fields for which ground information had been acquired in conjunction with the SAR mission. For the over-whelming majority of cases, the AX distribution is symmetrical and has a single major lobe centered at the mean value of the disstribution ¿¿ Whereas the mean AX was found to be close to zero degrees for bare soil, cut vegetation, alfalfa, soybeans, and clover, a different pattern was observed for the corn fields; the mean ¿¿ increased with increasing incidence angle 0 from about zero at 0 = 150 (near-range of the image) to about 140° at 0 = 35°. The explanation proposed for this variation is that the corn canopy, most of whose mass is contained in its vertical stalks, acts like a uniaxial crystal characterized by different velocities of propogation for waves with horizontal and vertical polarization. Thus, it is hypothesized that the observed backscatter is contributed by a combination of propagation delay, forward scatter by the soil surface, and specular bistatic reflection by the stalks. Model calculations based on this assumption were found to be in general agreement with the phase observations. View full abstract»

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  • Signature-Extendable Technology: Global Space-Based Crop Recognition

    Page(s): 93 - 103
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    A number of developments, such as those reported by Badhwar et al. [4], have resulted in a signature extendable technology. This technology, which we refer to as temporal profile technology, is simple and efficient and automatically recognizes crops by utilizing the Kauth-Thomas transform of Landsat, multidate data, and parameters derived from a model of each crop's greenness-time trajectory. These parameters have overcome the lack of crop separability and stability encountered with technology utilizing spectral values of individual Landsat bands. The temporal profile technology was able, without manual intervention or retraining, to classify Landsat MSS data and estimate within 3 percent the area of corn and soybeans within 5 x 6 nm segments over a large geographic region within the U. S. Corn Belt and Mississippi Delta for three crop years [ 5]. In this current paper we test this algorithm over a set of data in the Argentina corn and soybeans region, and show that it will, with at most minor modifications, apply directly to Argentina. Small-grains evaluations by Badhwar [ 5] and Lennington et al. [181] strongly indicate that the temporal profile technology will work well for that important crop group. We also develop a theoretical framework for signature extendability. We show that the feature space generated by the temporal profile parameters will satisfy two conditions, separability and identifiability, required for a signature-extendable technology and will apply to any group of crops in any region that differ in their seasonal cycles. View full abstract»

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  • Land-Use Mapping Using Edge Density Texture Measures on Thematic Mapper Simulator Data

    Page(s): 104 - 108
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    Texture analysis was performed as part of an investigation of the information content of Landsat Thematic Mapper (TM) imagery. High-altitude aircraft scanner imagery from the Airborne Thematic Mapper (ATM) instrument was acquired over central California and used to simulate TM data. Edge density texture images were constructed by computation of proportions of edge pixels in a 31×31 moving window on a near-infrared ATM band. A training technique was employed to select computational parameters to maximize the difference between edge density measurements in urban and in rural areas. The results of classification of the texture images showed that urban and rural areas could be distinguished with texture alone, indicating that inclusion of texture in automated classification procedures could significantly improve their accuracy. View full abstract»

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  • 1987-1988 Congredonal Fellowships a Congressional Internship for Members of IEEE

    Page(s): 114
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  • IEEE copyright form

    Page(s): 115 - [115]-a
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  • Information for authors

    Page(s): [115]b
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  • Institutional listings

    Page(s): 115c
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Aims & Scope

 

IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING (TGRS) is a monthly publication that focuses on the theory, concepts, and techniques of science and engineering as applied to sensing the land, oceans, atmosphere, and space; and the processing, interpretation, and dissemination of this information.

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Antonio J. Plaza
University of Extremadura