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Geoscience and Remote Sensing, 1997. IGARSS '97. Remote Sensing - A Scientific Vision for Sustainable Development., 1997 IEEE International

Date 3-8 Aug. 1997

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  • IGARSS'97 [front matter]

    Page(s): i - lxxi
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  • Conference Author Index

    Page(s): 0_4 - 0_11
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  • Snow accumulation on Greenland estimated from ERS scatterometer data

    Page(s): 1823 - 1825 vol.4
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    Radar cross section measurements over Greenland by the scatterometer of the European Remote Sensing satellites (ERS-1 and ERS-2) between August 1991 and March 1997 have been analysed. For large areas especially in the transition region between the percolation and dry-snow zone an almost linear decrease of up to 0.75 dB/year in normalized radar cross section was observed. This reduction can be attributed to increasing attenuation of the radar backscatter due to dry-snow accumulation on the firn of the percolation zone. A 2-layer radar backscatter model accounting for the measurement parameters of the ERS scatterometers and considering a firn layer buried by dry-snow was used to estimate the thickness of the dry-snow layer and to derive a snow accumulation rate. The spatial pattern and absolute values of accumulation rates so inferred agree well with recent synthesis of ground-based observations View full abstract»

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  • Algorithms for atmospheric correction for ocean color data

    Page(s): 1896 - 1898 vol.4
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    Atmospheric correction algorithms for ocean color data given by ADEOS/OCTS are shown. The authors' atmospheric correction is based on the radiative transfer process in an atmosphere-ocean model. In order to achieve better atmospheric correction, this paper proposes two subjects; one is how to determine aerosol characteristics by referring to polarization measurements, the other is new definition of atmospheric correction coefficients. It is found that an oceanic aerosol model with the log-normal size distribution of (r¯=0.24 μm, σ=2.0 μm) is a good candidate to describe the polarization data measured on July 29th in 1996 over the ocean in Seto Inland Sea in Japan. The authors also found that our atmospheric correction provides an improved chlorophyll map near the sea surface on September 3rd in 1996 View full abstract»

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  • Aerosol retrieval using synthetic POLDER multi-angular data

    Page(s): 1917 - 1919 vol.4
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    The POLarization and Directionality of the Earth's Reflectances (POLDER) instrument onboard the Japanese ADEOS satellite offers unique possibilities for the retrieval of aerosol parameters with its polarization and multi-angular capability. In this study the authors examine a technique that simultaneously retrieve multiple aerosol parameters, namely asymmetry factor, single-scattering albedo, surface albedo, and optical thickness, using simulated POLDER reflectances. It is found that, over dark or bright surfaces, simultaneous retrieval of multiple parameters is indeed possible, but not over surfaces with intermediate reflectivity. Among the four parameters, the single-scattering albedo is retrieved with the best accuracy and is the least vulnerable when the reflectance value is subjected to a 0.1% white noise View full abstract»

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  • Aerosol optical thickness and scattering phase function retrieval from solar radiances recorded over water: a revised approach

    Page(s): 1920 - 1922 vol.4
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    The possibility of deriving aerosol optical thickness and phase function values for certain scattering angles from solar radiances recorded over the oceans is examined. Radiative transfer simulations results for the Advanced Very High Resolution Radiometer (AVHRR) and the Moderate Resolution Imaging Spectrometer (MODIS) instruments are presented. These results indicate that an iterative procedure should be used for the simultaneous determination of the two quantities View full abstract»

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  • Construction of multi-resolution terrain models using hierarchical Delaunay triangulated irregular networks

    Page(s): 1999 - 2001 vol.4
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    For land planning or visualization, there is a need to model a large area of digital terrain in a graphics workstation and then display the 3D terrain model at a general frame rate. However, the geometrical complexity of terrain models far exceeds the capabilities of a general graphics workstation. Using a multi-resolution terrain model is one way to fit the requirement of the applications. Simplification or decimation algorithms are used to generate multiple terrain models at different detailed levels and then the models are selected to display for different situations such as distance or view scope. In this study, the authors concentrate on the triangulation and the level-of-detail generation of terrain models. In triangulation, they improve the performance of Palacios-and-Renuad triangulation algorithm. In level-of-detail generation, they give a new criterion to improve the accuracy of sequential multi-resolution terrain models based on the Schroder-and-Robbach, Schroeder et. al., and Floriani-and-Puppo approaches. They also propose a new hierarchical structure of Delaunay triangulated models to represent multi-resolution terrain models. The hierarchical structure is a tree structure, and thus result in a better search performance than other approaches View full abstract»

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  • An interferometric SAR processor avoiding phase ambiguities

    Page(s): 1713 - 1715 vol.4
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    One of the key problems in SAR interferometry is the determination of the absolute phase of a scatterer by unwrapping the calculated phase difference of two SAR images. Since the phase difference is a function modulo 2π software algorithm are used to perform a phase unwrapping to obtain an unambiguous phase and thus the corresponding height information. This paper presents a procedure using two different transmit frequencies to enlarge the unambiguous range for height determination. Measurements performed in an anechoic chamber are used to test the processing. Using this procedure it is not only possible to resolve the height of a surface but also of single scatterers in space or in urban areas with steep slopes View full abstract»

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  • Studying the monsoon circulation in the Indian Ocean using altimeter data

    Page(s): 1698 - 1700 vol.4
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    The oceanic variability in response to the monsoon system in the northern Indian Ocean was for the first time studied using the three altimeters Geosat, ERS-1 and Topex/Poseidon. The root mean square, computed from the sea surface height anomalies indicates values of 15-17 cm in highly energetic areas such as the Somali Current, and 13-15 cm in the western part of the Bay of Bengal. As the most prominent variations occur, and because most in situ observations are from these areas the investigation was focused on these two areas. Complex principal component analysis was applied to the gridded SSH anomalies and the results indicate that the annual signal is strongest when the monsoon period is at its peak, and the semi-annual time series seems to be related to the onset and decay phase of the SW and NE monsoon. CPCA analysis of the Topex/Poseidon data indicates characteristic periods of 40-50 days which are probably related to earlier observations in the study area of mesoscale variability generated by the horizontal shear in the velocity field. Westward propagating waves are identified from the annual and semi-annual modes, and they are observed to have a westward propagating speed of 13 km/d at the equator, with decreasing speed away from the equator. Mesoscale eddies with diameters between 250-1000 km and maximum amplitudes up to 45 cm are observed during the monsoon periods. The propagation and life time of eddies in the study area are in good agreement with those reported in previous investigations using in situ, data and numerical models View full abstract»

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  • Microwave measurements of sea ice in the Kara and Laptev Sea

    Page(s): 1675 - 1677 vol.4
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    Radiometric measurements made during the Arctic-expedition ARK 12 of R.V. Polarstern in the Kara and Laptev Sea which took place from 12th July to 23th September 1996 were obtained using three Dicke Radiometers from the University of Bern (Switzerland) mounted on a sledge operating at 11, 21 and 35 GHz and measuring in horizontal and vertical polarization with incidence angles between 20 and 70 degrees. The observed brightness temperatures show a strong correlation with the snow thickness. The size of the snow grains is also important. Some examples of the data set are compared to a combined radiative transfer-strong fluctuation theory approach using a layer model describing the sea ice and calculating the emissivities of both polarizations View full abstract»

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  • Development results of TRMM precipitation radar

    Page(s): 1630 - 1632 vol.4
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    A precipitation radar (PR) has been developed by the National Space Development Agency of Japan (NASDA) in cooperation with the Communication Research Laboratory (CRL). The PR was integrated into the Tropical Rainfall Measuring Mission (TRMM) satellite and TRMM satellite system testing is ongoing by NASA. Throughout the various tests of PR it was confirmed that the PR satisfies its requirements View full abstract»

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  • Estimation of adjacent effects in polarization measurements over the coastal zone

    Page(s): 1902 - 1904 vol.4
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    The polarization over the coastal zone observed by the airborne POLDER simulator, which was developed by CNES, France, is analyzed. It is shown that at the wavelength λ=850 nm, the polarization degrees over the coastal zone become smaller than those over the sea surface at a long distance from the land, while at λ=450 nm the polarization pattern over the coastal zone is almost the same as that over the sea surface distant from the land. In this study, the adjacency effect influence on polarization measurements is evaluated by using a single scattering radiative transfer model. As a result, it is found that at λ=850 nm, as adjacent effects arising from the radiation reflected by the land surface are more significant, the degree of polarization over the sea surface becomes smaller View full abstract»

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  • Internal waves detection from ERS-1 SAR images using the 2-D wavelet transform

    Page(s): 2069 - 2071 vol.4
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    The utility of wavelet analysis as a tool for automatic oceanic internal wave detection from SAR ocean images is examined using the 2D wavelet transform. A method for coastline detection based on a sequence of basic-processing procedures followed by a contour tracing algorithm is also introduced in order to have sea-land separation to enhance the internal wave detection problem. Then, the image is wavelet transformed with various scales to finally extract the internal wave structures based on the first and second order statistics. The results from this study show that wavelet analysis is an excellent tool to detect and locate internal waves from SAR ocean images against background noise View full abstract»

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  • Satellite remote sensing of fires, smoke and regional radiative energy budgets

    Page(s): 1923 - 1925 vol.4
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    Using satellite imagery, more than five million square kilometers of the forest and cerrado regions over South America are extensively studied to monitor fires and smoke during the 1985 and 1986 biomass burning season. The results are characterized for four major ecosystems, namely: (1) Tropical Rain Forest [TRF], (2) Tropical Broadleaf Seasonal [TBS], (3) Mild/Warm/Hot Grass/Shrub [MGS], and (4) Savanna/Grass and Seasonal Woods [SGW]. Using collocated measurements from the instantaneous scanner Earth Radiation Budget Experiment (ERBE) data, the direct regional radiative forcing of biomass burning aerosols are computed. The results show that more than 70% of the fires occur in the MGS and SGW ecosystems due to agricultural practices. The smoke generated from biomass burning has negative net radiative forcing values for all four major ecosystems within South America. The smoke found directly over the fires have mean net radiative forcing values ranging between -25.6 to -33.9 W/m2 for 1985 and between -12.9 to -40.8 W/m2 for 1986. These results confirm that the regional net radiative impact of biomass burning is one of cooling View full abstract»

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  • Incorporating remotely-sensed land surface parameters in a land surface parameterization

    Page(s): 1509 - 1511 vol.4
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    Sensitivity studies are conducted with a land surface parameterization (LSP) to investigate the impact of remotely sensed land surface parameters (leaf area index (LAI), roughness length, albedo) on modeled surface fluxes. The incorporation of albedo and LAI in the LSP are found to significantly modify the simulated surface fluxes View full abstract»

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  • A comparison of surface current fields derived by beam forming and direction finding techniques as applied by the HF radar WERA

    Page(s): 1805 - 1807 vol.4
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    HF radar in oceanography makes use of backscattering of electromagnetic waves of 10 m to 50 m wavelength from the rough sea surface to measure surface current and ocean wave parameters. In Germany, the work on ground wave HF radar started in 1980, adopting NOAA's CODAR (COastal raDAR). Recent developments within the European project SCAWVEX (Surface Current And Wave Variability Experiment) lead to a new design called WERA (WEllen RAdar). In Spring 1996, two WERA and CODAR systems have been deployed north and south the Rhine mouth at the Dutch coast. While CODAR uses a four-element squared receive antenna array and direction finding technique for azimuthal resolution, WERA in addition can be configured to use a linear array and beam forming. As both systems have been operated simultaneously at the same location, comparisons of the surface current fields measured by the different systems and algorithms are possible. By defining an absolute quality criterion based on spectral analysis of current time series, limitations in the direction finding algorithm concerning ship traffic can be identified View full abstract»

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  • Efficient simulation of SAR interferometric raw signal pairs

    Page(s): 1701 - 1703 vol.4
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    An efficient SAR raw signal simulator of cross-track interferometric pairs is presented. It is based on the physical optics evaluation of the scattering contributes and it is efficiently implemented via an analytic formulation of the SAR system transfer function. A certain number of meaningful examples are also presented and discussed View full abstract»

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  • First realtime use of RADARSAT SAR imagery for ship navigation in Antarctica

    Page(s): 1678 - 1680 vol.4
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    In polar regions, navigation strongly depends on ice conditions which can be defined by ice types and ice concentration. For a long time, satellite imagery, specially AVHRR and SAR data, has been providing such information. Henceforth, until now the availability of SAR images for ship navigation in Antarctica was not sufficient for this data to be used in a realtime approach. However, due to its onboard recorder, the Canadian satellite, RADARSAT, can acquire images over Antarctica on a regular basis. The experiment presented in this paper investigates its potential for ship routing to Antarctica and, in particular, towards the Dumont d'Urville French Polar Station View full abstract»

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  • Identifying and monitoring change in wetland environments using SAR

    Page(s): 1573 - 1575 vol.4
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    The potential of synthetic aperture radar (SAR) to map the distribution of wetlands, forests and woodlands and to monitor long term developments in these ecosystems, as well as to contribute to an understanding of global change, depends on the ability of science to unravel the relationships that exist between microwave backscatter, surface conditions and the physical characteristics of trees and forests. Four major research programs are currently being undertaken in tropical Northern Australia incorporating the analysis of SIR-C/X SAR; ERS 1/2; RADARSAT and AIRSAR data along with Landsat TM and SPOT imagery. These are: Investigating the backscatter properties and dynamics of Australian tree types and forests (with Dong and Forster). Monitoring change in coastal wetlands, forests and woodlands in Northern Australia using RADARSAT (with Finlayson). Characterisation of vegetation and land surfaces on intertidal flats in Northern Australia using radar (with Adam and King). Remotely sensed indicators of habitat heterogeneity and biological diversity: Kakadu World Heritage Region, Northern Australia (with Imhoff and Sisk) View full abstract»

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  • Radiometric estimates of grain yields related to crop Aboveground Net Production (ANP) in paddy rice

    Page(s): 1793 - 1795 vol.4
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    Crop aboveground net production (ANP) is a major factor for determining the total biomass and closely related to the amount of grain production at each development state. Spectral reflectance was measured in paddy field (Ilpum var.) to interpret grain yield from satellite image using the relations between agronomic parameters such as LAI and ANP. LANDSAT TM equivalent band set was created by integrating measured spectral reflectance values to the real TM band range. The authors made polynomial functions of spectral reflectance on two wavelength ranges, VIS (0.50-0.68 μm) and NIR (0.69-1.00 μm), of each development state. As a result of correlation analysis between the LANDSAT TM equivalent bands, agronomic parameters, and multi-channel vegetation indices, both ANP and LAI of paddy rice could be estimated by TM equivalent bands and vegetation indices, functionally. Rice ANP and LAI can be estimated from spectral measurements. These estimates can then be used to forecast final grain yield View full abstract»

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  • On the measurement of stratus cloud properties with a cloud radar and microwave radiometer

    Page(s): 2090 - 2092 vol.4
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    Algorithms have been developed to calculate the vertical profiles from cloud radar reflectivity measurements and microwave radiometer measurements of integrated liquid water. In addition, the algorithms calculate the effective radius profiles, and the total number of cloud droplets. When drizzle is present, radar reflectivity, vertical velocity and the spread of the vertical velocity can be used to calculate vertical profiles of liquid water, liquid water flux, effective radius, and droplet number. When there is no drizzle, the authors can use the Doppler capability to profile various vertical velocity turbulence parameters, such as the vertical velocity spectra, variance, and skewness. All parameters are important in the development of cloud models. Data taken during ASTEX (Atlantic Stratocumulus Transition Experiment) have been used to study the behavior of stratus clouds at Porto Santo Island, Madeira, Portugal View full abstract»

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  • Assessment of scatterometer data for environmental studies in Thar desert

    Page(s): 1829 - 1831 vol.4
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    Since summer 1991 the scatterometer aboard European Remote Sensing Satellites ERS-1 and ERS-2 have provided global radar backscatter measurements of the Earth's surface. Over the oceans, these data are used operationally for wind field retrieval. Simultaneously possible applications of these low resolution data over land surfaces were studied by numerous investigators. Due to the global coverage, the continuity of the data and the wide range of incidence angle these data have been found to provide valuable information despite the coarse resolution. The authors analyze normalized radar cross section (NRCS) measurement obtained over Thar desert in Pakistan between May 1994 and May 1996. Spatial variations in the radar cross section are compared with vegetational and meteorological parameters. Seasonal as well as interannual variations are investigated by correlating the radar backscatter with phenological, meteorological and AVHRR NDVI data. Zonal characterization of area is made on the basis of backscatter behavior and meteorological data. The geophysical parameters of the land are reflected in the incidence angle diversity of the ERS scatterometer. It is demonstrated that valuable information can be delineated from the ERS scatterometer data over arid regions in order to provide data for environmental and especially climatic monitoring View full abstract»

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  • A study of the effect of swell in scatterometer wind measurements using ERS SAR wave mode data

    Page(s): 1512 - 1514 vol.4
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    Coincident and nearly co-located SAR wave mode data and scatterometer data are used to study the effect of swells in the ERS scatterometer measurements. It is shown that the speckle power in the SAR wave mode spectrum is a good measure of the mean radar backscatter from the ocean surface. The wind dependence of the speckle power is compared with the scatterometer winds with and without the effects of swell. It is shown that the speckle power increases in the presence of swell. The swells travelling in the azimuth direction have a greater impact on the speckle power than range travelling swells. It is argued that the wind speed dependence of the SAR speckle power enables the SAR to be used as a high resolution wind mapper View full abstract»

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  • Operational generation of AVHRR-based level-3 products at the German Remote Sensing Data Centre: status and perspectives

    Page(s): 1505 - 1508 vol.4
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    The German Remote Sensing Data Centre (DFD) of the German Aerospace Research Establishment (DLR) has been operating a ground segment for High Resolution Picture Transmission (HRPT) data acquisition, archiving, and distribution since the early 1980s. The station's visibility covers all of Europe. DFD started with the generation of thematic level-3 AVHRR value-added products consisting of Multichannel Sea Surface Temperatures (MCSST) and Normalized Difference Vegetation Indices (NDVI) in March 1993. Additionally, calibrated and registered 5-channel image subsets in two areas have been generated for supporting user-specific applications since 1994. The status of the current level-3 product generation chain as well as corresponding processing algorithms are presented. Perspectives to improve the existing products in terms of channel 1 and 2 radiometric optimization by implementing of a pre-operational atmospheric correction scheme developed by, as well as possibilities to correct the solar channels for anisotropic reflectance with respect to different surfaces are shown. Further, new level-3 products such as geophysical cloud parameters derived using the APOLLO algorithm are presented. Also, first results from various algorithm tests are presented to define an operational land surface temperature (LST) product by estimating surface emissivity based on NDVI time profiles View full abstract»

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  • Results of CAL/VAL and preliminary scientific results of ADEOS

    Page(s): 2072 - 2074 vol.4
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    ADEOS was successfully launched on August 1996. It carries 8 sensors on board to measure the atmosphere, ocean and land surface for better understanding of global change. The spacecraft and all the 8 sensors on board are functioning well and good scientific results can be expected. Initial calibrations of most of the sensors are finished and performances are the same or better than expected View full abstract»

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