• Proceedings of the KSRS Conference
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• 1999.11a
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• pp.154-157
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• 1999

Microwave polarimetric backscattering from a wet soil surface had been measured using a Ku-band polarimetric scatterometer at the incidence angles ranging from 10$^{\circ}$ to 70$^{\circ}$ Since the accurate target parameters as well as the radar parameters are necessary for radar scattering modeling, a complete and accurate set of ground truth data were also collected, from which accurate measurements were made of the rms height, correlation length, and dielectric constant. The measured polarimetric backscattering coefficients (vv-, hh-, vh-, hv-polarizations) were compared with theoretical models and empirical models. A new semi-empirical model for microwave polarimetric radar backscattering from bare soil surfaces was developed using polarimetric radar measurements and the knowledge based on the theoretical and numerical solutions. The model was found to yield very good agreement with the backscattering measurements of this study.

• Journal of electromagnetic engineering and science
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• v.5 no.4
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• pp.183-188
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• 2005

A simple microwave backscattering model for vegetation canopies on earth surfaces is developed in this study. A natural earth surface is modeled as a two-layer structure comprising a vegetation layer and a ground layer. This scattering model includes various scattering mechanisms up to the first-order multiple scattering( double-bounce scattering). Radar backscatter from ground surface has been modeled by the polarimetric semi-empirical model (PSEM), while the backscatter from the vegetation layer modeled by the vector radiative transfer model. The vegetation layer is modeled by random distribution of mixed scattering particles, such as leaves, branches and trunks. The number of input parameters has been minimized to simplify the scattering model. The computation results are compared with the experimental measurements, which were obtained by ground-based scatterometers and NASA/JPL air-borne synthetic aperture radar(SAR) system. It was found that the scattering model agrees well with the experimental data, even though the model used only ten input parameters.

• Korean Journal of Remote Sensing
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• v.10 no.2
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• pp.17-35
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• 1994

A semi-empirical model for microwave polarimetric radar backscattering from bare soil surfaces was developed using polarmetric radar measurements and the knowledge based on the theoretical and numerical solutions. The microwave polarimetric backscatter measurements were conducted for bare soil surfaces under a variety of roughness and moisture conditions at L-, C-, and X-band frequencies at incidence angles ranging from 10` to 70`. Since the accrate target parameters as well as the radar parameters are necessary for radar scattering modeling, a complete and accurate set of ground truth data were also collected using a laser profile meter and dielectric probes for each surface condition, from which accurate measurements were made of the rms height, correlation length, and dielectric constant. At first, the angular and spectral dependencies of the measured radar backscatter for a wide range of roughnesses and moisture conditions are examined. Then, the measured scattering behavior was tested using theoretical and numerical solutions. Based on the experimental observations and the theoretical and numerical solutions, a semi-empirical model was developed for backscattering coeffients in terms of the surface roughness parameters and the relative dielectric constant of the soil surface. The model was found to yield very good agreement with the backscattering measurements of this study as well as with independent measurements.

• Proceedings of the KSRS Conference
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• 1998.09a
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• pp.180-185
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• 1998

Microwave polarimetric backscattering from a various types of grassland canopies has been analyzed by using the first-order radiative transfer theory in this paper. Leaves in the grassland are modeled by rectangular resistive sheets, which sizes (widths and lengths) and orientations (elevation and azimuth angles) are randomly distributed. Surface roughness and soil moisture of the ground plane under the grass canopy is considered in this computation. The backscattering coefficients of grasslands are computed for different radar parameters (angles, frequencies and Polarizations) as well as different canopy Parameters (size and orientation distributions of leaves, canopy depth, moisture contents of leaves and soil, rms height and correlation length of soil surface). A radar system for 15GHz has been fabricated and used for measurement of the scattering coefficient from a grass canopy. The computation result obtained by the scattering model for the grass canopy is compared with the measurements.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.9 s.112
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• pp.804-810
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• 2006

In this paper, we describe a measurement technique for the backscattering coefficient and ground truth of a vegetation canopy in detail. A simple microwave backscattering model for vegetation canopies is verified by being compared with this measurement. An R-band$(1.7\sim2.0GHz)$ scatterometer system is used to measure the backscattering coefficient of a vegetated area in the Han-river park for various incidence angles and a wide range of the soil moisture contents. It is found that the model agrees quite well with the measurements for co-polarized radar backscatter, and needs a correction for cross polarized radar backscatter.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.5
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• pp.763-772
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• 2000

The Radiative Transfer Model(RTM) for computation of microwave polarimetric backscattering coefficients of a various types of vegitation canopies has been examined in this paper. Leaves in the vegitation canopy are modeled by rectangular resistive sheets, which sizes and orientations are randomly distributed. Surface roughness and soil moisture of soil surface are considered in this computation. The backscattering coefficients of grasslands are computed for various values of radar parameters and canopy parameters. A polarimetric scatterometer radar system at 15 GHz has been used for measurement of the scattering coefficient from a grass canopy and a cabbage canopy. The computation results obtained by the RTM for the canopies are compared with the measurement for examination of the RTM.

• Korean Journal of Remote Sensing
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• v.4 no.1
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• pp.1-16
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• 1988

Multiyear ice is quite thick in general, and it needs to be distinguished from thinner types of ice because it represents a severe navigational hazard. Here, models are described for the radar backscatter from multiyear sea ice, based on simple scattering layers. Under cold conditions, the radiative transfer volume-scatter model can describe the backscattering from multiyear ice for frequencies higher than about X-band, while the surface scattering contribution has to be included for lower frequencies. A simple semi-empirical model is shown to be a good approximation to the radiative transfer model in describing the volume scattering from multiyear ice.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.316-318
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• 2003

An eigen-analysis of the coherency matrix provides the polarimetric scattering mechanisms with the matrix characterizing parameters. In this paper, the coherency matrices of deciduous and coniferous vegetation are calculated using the analytical method. The Generalized Rayleigh-Gans approximation is used to model backscattering from distributed coniferous and deciduous leaves. The characteristics of eigen-parameters of simulated coherency matrix for deciduous and coniferous leaves with respect to the leaf shapes and orientations are illustrated.

• Journal of the Korean earth science society
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• v.40 no.5
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• pp.447-463
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• 2019

Sea surface wind is a fundamental element for understanding the oceanic phenomena and for analyzing changes of the Earth environment caused by global warming. Global research institutes have developed and operated scatterometers to accurately and continuously observe the sea surface wind, with the accuracy of approximately ${\pm}20^{\circ}$ for wind direction and ${\pm}2m\;s^{-1}$ for wind speed. Given that the spatial resolution of the scatterometer is 12.5-25.0 km, the applicability of the data to the coastal area is limited due to complicated coastal lines and many islands around the Korean Peninsula. In contrast, Synthetic Aperture Radar (SAR), one of microwave sensors, is an all-weather instrument, which enables us to retrieve sea surface wind with high resolution (<1 km) and compensate the sparse resolution of the scatterometer. In this study, we investigated the Geophysical Model Functions (GMF), which are the algorithms for retrieval of sea surface wind speed from the SAR data depending on each band such as C-, L-, or X-band radar. We reviewed in the simulation of the backscattering coefficients for relative wind direction, incidence angle, and wind speed by applying LMOD, CMOD, and XMOD model functions, and analyzed the characteristics of each GMF. We investigated previous studies about the validation of wind speed from the SAR data using these GMFs. The accuracy of sea surface wind from SAR data changed with respect to observation mode, GMF type, reference data for validation, preprocessing method, and the method for calculation of relative wind direction. It is expected that this study contributes to the potential users of SAR images who retrieve wind speeds from SAR data at the coastal region around the Korean Peninsula.