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Geoscience and Remote Sensing Symposium, 1993. IGARSS '93. Better Understanding of Earth Environment., International

Date 18-21 Aug. 1993

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Displaying Results 1 - 25 of 618
  • Proceedings of IGARSS '93 - IEEE International Geoscience and Remote Sensing Symposium

    Publication Year: 1993
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    Freely Available from IEEE
  • Frequency modulated Doppler radar for scatterometry and surface profiling

    Publication Year: 1993 , Page(s): 1637 - 1640 vol.4
    Cited by:  Papers (5)
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    A Doppler coherent combined scatterometer and ground surface profiler is analyzed. The HF-oscillator transmits a periodic saw-tooth or triangular frequency modulation. The reflected signal from the ground is detected by a homodyne receiver. As a result of the periodic frequency modulation, the IF-spectrum at the mixer output has strong components at harmonics of the modulation frequency, which are split up into Doppler side-bands when the radar is moving. The relative energy content of each tone mainly depends upon the frequency excursion of the frequency modulation and the distance from the reflector. By combining the amplitude information of two different tones, both scatterometry measurements and surface profiling from a moving platform are made possible View full abstract»

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  • A mathematical monitoring concept in an Earth observation framework

    Publication Year: 1993 , Page(s): 1707 - 1709 vol.4
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    In a multidisciplinary field like Earth observation, not only assessment but also the monitoring of processes is important. Assessment is defined as the arrangement of objects in classes through characteristic attributes at a certain moment in time, whereas monitoring is defined as the detection of changes of objects explicitly using existing knowledge and constraints. This distinguishes monitoring from assessment. A mathematical description of assessment and monitoring forms the basis for a generic monitoring concept, The concept shows clearly the interaction and differences between assessment and monitoring. Within the Earth observation framework it is evident that the monitoring concept can be justified against repeated assessment. Two practical examples will be presented, showing the implications of the monitoring concept for the monitoring of deforestation and the monitoring of military infrastructures and activities View full abstract»

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  • Modeling of radar responses to forest physical parameters

    Publication Year: 1993 , Page(s): 384 - 386 vol.2
    Cited by:  Papers (1)
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    The objective of the study was to investigate the relationship between radar response and forest parameters, i.e. stem density, tree height and biomass. Field measurements of trees and the underlying soil surface of a conifer forest stand were used in modeling of radar backscattering from 100 simulated forest stands with average tree height and stem density randomly generated within specified ranges (height from 2 to 20 meters, stem density from 10 to 3400 trees/ha). The modeling results were also compared with measured backscatter from stands in Maine, USA. The results show that radar return is more sensitive to tree height than to stem density. The total biomass has much higher correlation to the radar return than to tree height or stem density alone. Modeling results also show that the cross-polarization return at a longer wavelength has the best correlation with forest physical parameters View full abstract»

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  • Airborne lidar measurements of ozone, water vapor, and aerosols in large-scale atmospheric studies

    Publication Year: 1993 , Page(s): 865 - 868 vol.2
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    The NASA Langley Research Center's airborne DIfferential Absorption Lidar (DIAL) systems have been used to study large-scale atmospheric distributions of ozone, water vapor, and aerosols in 12 international field experiments over the last 13 years. This paper describes the authors' airborne DIAL systems and discusses recent measurements of ozone and aerosol distributions in the summertime troposphere over the western Pacific and in the wintertime Arctic stratosphere. Airborne DIAL measurements of tropospheric water vapor and aerosol distributions during the daytime and nighttime are also discussed View full abstract»

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  • A near-realtime geolocated and radiometric corrected low-resolution ERS-1 SAR image product

    Publication Year: 1993 , Page(s): 2125 - 2126 vol.4
    Cited by:  Papers (2)
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    An operational algorithm is developed and implemented for geolocation and radiometric correction of the near-realtime low-resolution ERS-1 SAR image product from Tromso Satellite Station (TSS). Latitude and longitude grids and land-contours are mapped into the image. The radiometric correction adjusts the pixel intensity for varying antenna gain across the swath and range spreading loss. The antenna gain is based on the ESA obtained in-flight ERS-1 SAR antenna pattern. The computing time exclusive the SAR processing, which roughly takes 6 minutes on the TSS SAR processor, is only about 1-2 minutes on a Sun Sparc 2 computer View full abstract»

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  • Use of Landsat TM imagery for updating forest cover information on Mount Elgon Forest Reserve in Uganda on the Kaproron 1:50,000 map sheet

    Publication Year: 1993 , Page(s): 2047 - 2049 vol.4
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    Detection of deforestation for updating maps with TM data is described. The deforestation process in Uganda and, in East Africa as a whole, has increased since 1970s. Mount Elgon Forest Reserve is one of the many forests in the country which are subjected to land, population and socio-economic pressure being threatened with total destruction. In this study, Landsat TM data is examined for its potential to provide reliable information for monitoring forest cover area and updating the Kaproron Map. Results showed a reduction of 27% of forest cover area in 27 years. Agricultural encroachment was the main cause for destruction of natural forest followed by re-afforestation. The study illustrated the importance of TM data as a source of information of forest cover status, capable of updating maps at 1:50,000 View full abstract»

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  • Evaluation of the potential of the GER airborne imaging spectrometer for marine application

    Publication Year: 1993 , Page(s): 491 - 493 vol.2
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    The GER Imaging Spectrometer data is evaluated for remote measurement of optical properties of turbid (case 2) waters of coastal New Jersey. The spectral characterization of these waters is mainly produced by the organic, inorganic and dissolved organic matter. Measuring the spatial distributions of these components will provide an important tool to safeguard the water quality and ecosystem health of the estuarine/nearshore environment. Spectral absorption and scattering estimated through analysis of the airborne hyperspectral data will be used for water quality model development. Such developmental use will aid the forthcoming transition to the next generation of spaceborne systems (i.e. MODIS) for oceanic and global measurements of primary productivity. This is considered to be a major pathway of carbon cycling in the ocean and thus essential to global change studies View full abstract»

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  • A Doppler spectral method of identifying water and ice in marginal-ice-zone imagery

    Publication Year: 1993 , Page(s): 441 - 444 vol.2
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    Complex synthetic aperture radar (SAR) imagery at C-band and X-band were acquired in and near the marginal-ice-zone on March 26 1989 in the Greenland Sea. The authors specially process this imagery to obtain Doppler spectra from two backscatter regions: (1) newly forming ice inside a tongue shaped region called the Odden and (2) open water adjacent to the Odden. They observe Doppler bandwidth broadening from the water imagery compared to the spectral width backscattered from the ice. A model is developed describing this broadening in terms of the platform motion, and the short and long ocean waves. They claim this broadening is primarily due to random sub-resolution velocities within a SAR resolution cell caused by the short ocean waves. The bandwidth broadening is extracted as Δfˆa≈40 Hz at C-band and Δfˆa≈55 Hz at X-band. The corresponding scene correlation times are 2τc≈22 ms at C-band and 16 ms at X-band. The measured ice bandwidth due to the platform motion (155 m/s) is approximately 118 Hz at both C-band and X-band View full abstract»

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  • The determination of sea surface wind and temperature with airborne radiometric data

    Publication Year: 1993 , Page(s): 1622 - 1624 vol.4
    Cited by:  Papers (5)
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    Deals with preliminary results of the Joint US/Russia Internal Wave Remote Sensing Experiment (PreCHERI). The airborne radiometric (RM) complex and side-looking real aperture radar (RAR) are briefly described. The algorithms of sea surface temperature and surface wind restoration from RM data are outlined. The results of reconstruction are compared with true surface data. The standard deviation for wind direction is ΔΦ=5.3°(for wind speed Δv=0.43 m/s; and for temperature ΔT=0.38 degC). The comparison of RH data with RAR pictures shows a good agreement of backscatter in VV-polarization with the value of polarizational anisotropy in RM channels. It is concluded that combined analysis of RM and RAR data enables significantly improved algorithms to be developed for ocean remote monitoring View full abstract»

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  • Classification of multispectral imagery using dynamic learning neural network

    Publication Year: 1993 , Page(s): 896 - 898 vol.2
    Cited by:  Papers (1)
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    The paper presents the results of classification of SPOT high resolution visible (RHV) multispectral imagery using neural networks. The test site, located near Taoyuan county of the northern Taiwan, is an agriculture area containing small ponds, bare and barren soils, vegetation, built-up land, near shore sea, and man-made buildings. The classifier is a dynamic learning neural network (DL) using the Kalman filter technique as an adaptation rule. The network architecture involves multi-layer perceptrons, i.e., feed-forward nets with one or more layers of nodes between the input and output nodes. The methodology of selection of training data sets is addressed. Then, accordingly, selected data sets from a 512×512 pixels three-band image are used to train the neural nets to categorize different types of the land-cover. Both simulated and real images are used to test the classification performance. Results indicate that the DL substantially reduces the training time as compared to the commonly used back-propagation (BP) trained neural network whose slow training process is shown to impede it in certain practical applications. As for classification accuracy, the presented results are shown to be excellent. It is concluded that the use of a dynamic learning network gives very promising classification results in terms of training time and classification accuracy. In particular, the proposed network significantly improves the practicality of the land-cover classification View full abstract»

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  • Results from inverting ERS-1 SAR image mode data into directional ocean wave spectra

    Publication Year: 1993 , Page(s): 16 - 18 vol.1
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    Results from validating the ocean wave spectra derived from ERS-1 SAR image mode data are presented. The wave spectra are obtained by combining numerical wave model data with SAR data in an inversion process. The validation is performed using in-situ reference data provided by directional and non-directional wave buoys. A variety of sea-states are considered including a hurricane with significant waveheight around 9 m. Significant wave height, peak wave direction and length are extracted from the in-situ and the SAR derived wave spectra, and compared with each other. Best agreement is observed for the peak wavelength. The large deviation in peak wave direction observed in some cases for the wind modes are explained by the limited along track resolution of the SAR instrument. The observed deviations in significant waveheight (at most 40%) are explained by an imperfect RAR modulation transfer function. However, in most cases the agreement is good as can be seen from the graphical presentation View full abstract»

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  • On radar polarimetry in FM-CW radar

    Publication Year: 1993 , Page(s): 368 - 370 vol.2
    Cited by:  Patents (1)
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    This paper attempts to apply the principle of radar polarimetry to wideband synthetic aperture FM-CW radar and presents a basic polarimetric detection result of a linear target in a laboratory measurement. Although the principle of radar polarimetry has well been established for the completely polarized wave and for the monostatic case, it still needs to be extended to wideband radar system. The FM-CW radar utilizes a wideband signal and the resultant beat signal whose frequency is proportional to range is different from the scattered wave in pulse radar. This paper points out that the Fourier transformed complex beat spectrum obtained by an synthetic aperture FM-CW radar acts like an element of the scattering matrix which plays the most important role in polarimetric imaging. The fact was verified by a polarimetric detection in a laboratory, demonstrating the validity of FM-CW radar polarimetry and indicating an establishment of a full polarimetric and synthetic aperture radar system View full abstract»

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  • Optical properties for sea ice measured during LEADEX '92

    Publication Year: 1993 , Page(s): 859 - 861 vol.2
    Cited by:  Papers (1)
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    A green laser, Ne:YAG (532 nm), was used to make both in situ and field laboratory measurements of transmission loss and spreading through samples of sea ice and snow collected from the Beaufort Sea during the LEADEX '92 experiment. The sea ice types sampled include first year (FY), multiyear (MY), melt pond (MP), and various stages of young lead ice (LD). Laboratory samples were taken from cores and placed in the collimated beam of the field portable instrument where losses and spreading were measured with a linear photodetector array. Comparable in situ measurements were made on lead ice and first year ice types by placing the laser source beneath the ice sheet and measuring the transmission and the beam spread function (BSF) at the surface. Data generated from both techniques were analyzed to characterize intrinsic beam transmission and small angle scattering optical properties View full abstract»

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  • Extraction of soil moisture from multitemporal, ERS-1 SLC data of the Freiburg test-site

    Publication Year: 1993 , Page(s): 1794 - 1796 vol.4
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    During May-October 1991 intensive ground-data collection was carried out on four fields to continuously record soil moisture in different depths and to measure weekly agricultural plant parameters (LAI, biomass, height) of different crops. The high temporal resolution of the radar data of almost 3 days during the Commissioning Phase of ERS-1 in 1991 enables the continuous documentation of the change of radar backscatter with changing surface features. Correlations were calculated between the different plant- and soil-parameters and the averaged backscatter from the fields under investigation. A high correlation coefficient of 0.8 was achieved between soil moisture and the grey-values of the test fields in the radar image. The correlation was independent of vegetation cover, and no correlation could be found between plant parameters and the grey-values View full abstract»

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  • Remote sensing of high temperature on the slope of Mt. Unzen-Fugendake volcano by infrared thermometer

    Publication Year: 1993 , Page(s): 2119 - 2122 vol.4
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    A remote sensing method was applied for estimating temperatures on the slope of Unzen-Fugendake volcano by a visual type infrared thermometer. The maximum values of surface temperatures on the northeast slope were 195°C on 18 October 1991, 138°C on 13 March 1992 and 134°C on 22 January 1993. The surface areas of elevated temperature (>50°C) were estimated to be 149000 m2 on 18 October 1991 and 99000 m2 on 22 January 1993. The maximum values of surface temperatures on the east slope were 131°C on 18 October 1991, 215°C on 13 March 1992 and 185°C on 22 January 1993. The surface area of elevated temperature (>100°C) were estimated to be 956000 m2 on 8 January 1992, 632000 m2 on 3 April 1992 and 62000 m2 on 22 January 1993. The high temperature area (>1OO°C) expanded rapidly due to pyroclastic flows. The decreasing rate of surface temperatures of pyroclastic flow were 3.9°C/min in the period of 2~12 minutes after the pyroclastic flow and 2.4°C/min in the period of 17-24 minutes View full abstract»

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  • On the application possibilities of spatial spectral analysis in the problems on state estimation of natural objects

    Publication Year: 1993 , Page(s): 2043 - 2044 vol.4
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    The spatial spectrum is proposed to be used for the remote identification of natural objects. Monodimensional spatial spectra of various types of underlying surface were estimated. The accuracy of the results are discussed View full abstract»

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  • Automatic detection of large object features from SAR data

    Publication Year: 1993 , Page(s): 1225 - 1227 vol.3
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    The feature extraction operation, from SAR images, encounters many difficulties due to the high level of noise and the poor quality of the object contour. This paper aims towards an implementation of an automated algorithm for extracting features of large objects such as rivers, lakes, or highways from SAR imagery. The method uses a watershed algorithm to detect homogeneous areas. The above areas are then grouped into probable objects using heuristic reasoning about the similarity between neighbouring regions and the difference between larger background areas. Results from SAR images of the Ottawa area are given View full abstract»

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  • An assessment of some small window-based spatial features for land-cover classification

    Publication Year: 1993 , Page(s): 1668 - 1670 vol.4
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    Fourteen small (3×3) window-based spatial measures are applied to a SPOT HRV multispectral Band 3 image to extract spatial features for the rural-urban fringe of Metropolitan Toronto, Canada. The spatial features are combined with the original image to identify 12 land-cover classes. Four classifiers were used in the study. Results show that when nine of the spatial features are in turn combined with the three original images, significantly improved classification accuracies (at the 95 percent confidence level) are obtained compared with using only the multispectral information from the three original images View full abstract»

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  • Radar scattering from snow facies of the Greenland ice sheet: results from the AIRSAR 1991 campaign

    Publication Year: 1993 , Page(s): 1270 - 1272 vol.3
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    In June 1991, the NASA/Jet Propulsion Laboratory airborne SAR (AIRSAR) collected the first calibrated multi-channel SAR observations of the Greenland ice sheet. Large changes in radar scattering are detected across different melting zones. In the dry-snow zone, Rayleigh scattering from small snow grains dominates at C-band. In the soaked-snow zone, surface scattering dominates, and an inversion technique was developed to estimate the dielectric constant of the snow. The radar properties of the percolation zone are in contrast unique among terrestrial surfaces, but resemble those from the icy Galilean satellites. The scatterers responsible for the percolation zone unusual echoes are the massive ice bodies generated by summer melt in the cold, dry, porous firn. An inversion model is developed for estimating the volume of melt-water ice retained each summer in the percolation zone from multi-channel SAR data. The results could improve current estimates of the mass balance of Greenland, and could help monitor spatial and temporal changes in the strength of summer melt in Greenland with a sensitivity greater than that provided by altimeters View full abstract»

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  • Influence of phytoplankton pigments and bottom features for water quality and depth estimation

    Publication Year: 1993 , Page(s): 488 - 490 vol.2
    Cited by:  Papers (1)
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    In the field of coastal studies, water quality and water depth estimates are very important. However, an estimation of the pollution in the sea using point sampling techniques is very difficult. Further, bathymetric surveying of shallow water areas by conventional ship-board sounding is slow and dangerous and needs expensive devices such as a sonar and a ship with very shallow draught. As a result, optical remote sensing is considered View full abstract»

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  • Analysis and simulation for a spotlight-mode aircraft SAR in circular flight path

    Publication Year: 1993 , Page(s): 1777 - 1780 vol.4
    Cited by:  Papers (1)
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    A spotlight-mode aircraft SAR in a circular flight path can efficiently obtain an image with very high azimuth resolution or a wider azimuth viewing angle. An analysis of this spotlight-mode SAR is made regarding the required PRF, the predicted resolution, and the computation complexity as a function of the aircraft altitude and the distance between the target and the center of the flight path projection. An efficient processing algorithm based on the exact wide beam spectrum is presented. The results of simulation indicate that the impulse responses meet the predicted resolution performance View full abstract»

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  • Oil spill detection in SAR imagery

    Publication Year: 1993 , Page(s): 943 - 945 vol.3
    Cited by:  Papers (7)
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    The possibilities for automatic segmentation of oil slicks and oil slick look-alikes in ERS-1 SAR imagery is investigated. “Spots” in the images are detected using adaptive thresholding and statistical classification of oil slick candidates is performed using geometric properties and gradient-based features. Promising results are shown, but the methods need to be tested on a larger data set before any final conclusions can be drawn View full abstract»

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  • The effect of topography on the SAR measurements of surface soil moisture

    Publication Year: 1993 , Page(s): 598 - 600 vol.2
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    The SIR-B (Shuttle Imaging Radar B) observations have established a good correlation between radar backscattering coefficient and surface soil moisture. Measurements from an airborne synthetic aperture radar (e.g., AIRSAR), on the other hand, have shown only a limited correlation between these parameters, even though a correction to allow for topographical variations was also attempted. This paper presents some new results from the AIRSAR flights over an agricultural area near Chickasha, Oklahoma. It was found that the changes in backscattering coefficients at P-, L-, and C-bands were, respectively, ~1-2 db, 2-3 db, and 5-6 db when soil moisture in the top 5-cm layer changed by ~0.13 g/cm3. The change in L-band backscattering coefficients was at least 3-4 db less than that observed by SIR-B. Two out of three AIRSAR C-band images also gave a higher backscattering coefficient at HH than VV polarization, which is not the case for images at P- and L-bands. These observed features may be related to problems in AIRSAR calibration View full abstract»

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  • Rain attenuation calculation using dielectric mixture with deformed rain drops

    Publication Year: 1993 , Page(s): 1250 - 1252 vol.3
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    A modified approach in computing the effective permittivity of a dielectric mixture, which takes into account the distributions in rain drop sizes, shapes and depolarization factors, has been used to obtain the rain-attenuation of both the horizontally and vertically polarized wave. The computed results agree well with those obtained from the more complicated Mie scattering theory. The differential attenuation of a horizontally and vertically polarized wave is obtained using the proposed model and compared favorably with Oguchi's result for the cases of rain droplets in the form of oblate spheroids and in a form described by Pruppacher and Pitter View full abstract»

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