• Korean Journal of Soil Science and Fertilizer
• /
• v.46 no.4
• /
• pp.237-244
• /
• 2013

Radar remote sensing is appropriate for monitoring rice because the areas where this crop is cultivated are often cloudy and rainy. Especially, Synthetic Aperture Radar (SAR) can acquire remote sensing information with a high temporal resolution in tropical and subtropical regions due to its all-weather capability. This paper analyzes the relationships between backscattering coefficients of rice measured by RADARSAT-2 SAR and growth parameters during a rice growth period. We examined the temporal variations of backscattering coefficients with full polarization. Backscattering coefficients for all polarizations increased until Day Of Year (DOY 222) and then decreased along with Leaf Area Index (LAI), fresh weight, and Vegetation Water Content (VWC). Vertical transmit and Vertical receive polarization (VV)-polarization backscattering coefficients were higher than Horizontal transmit and Horizontal receive polarization (HH)-polarization backscattering coefficients in early rice growth stage and HH-polarization backscattering coefficients were higher than VV-polarization backscattering coefficients after effective tillering stage (DOY 186). Correlation analysis between backscattering coefficients and rice growth parameters revealed that HH-polarization was highly correlated with LAI, fresh weight, and VWC. Based on the observed relationships between backscattering coefficients and variables of cultivation, prediction equations were developed using the HH-polarization backscattering coefficients.

• Current Optics and Photonics
• /
• v.2 no.2
• /
• pp.119-124
• /
• 2018

The errors in retrieved aerosol backscattering coefficients due to different lidar ratios are analyzed quantitatively in this paper. The actual calculation shows that the inversion error of the aerosol backscattering coefficients using the Fernald backward-integration method increases with increasing inversion distance. The greater the error in the lidar ratio, the faster the error in the aerosol backscattering coefficient increases. For the same error in lidar ratio, the smaller actual aerosol backscattering coefficient will get the larger relative error of the retrieved aerosol backscattering coefficient. The errors in the lidar ratios for dust or the cirrus layer have great impact on the retrievals of backscattering coefficients. The interval between the retrieved height and the reference range is one of the important factors for the derived error in the aerosol backscattering coefficient, which is revealed quantitatively for the first time in this paper. The conclusions of this article can provide a basis for error estimation in retrieved backscattering coefficients of background aerosols, dust and cirrus layer. The errors in the lidar ratio of an aerosol layer influence the retrievals of backscattering coefficients for the aerosol layer below it.

• Proceedings of the KSRS Conference
• /
• v.1
• /
• pp.446-449
• /
• 2006

It is backscattering of solar radiation by water body that makes ocean color observable from above, either by airplanes or satellites. Given the very low direct contribution to backscattering by phytoplankton cells, it is curious why the retrieval of phytoplankton concentration from remotely observed ocean color is evidently successful. From semianalytical bio-optical models, a dataset is created of spectral absorption, scattering and backscattering coefficients as a function of chlorophyll concentration. Four scenarios are considered, 1) only molecular and no particle scattering, 2) random particle backscattering uncorrelated with chlorophyll concentration, 3) constrained random particle scattering with known backscattering ratio, and 4) constrained random scattering with random backscattering ratio. Scenario 1 only introduces moderate errors of -20% - 90%. And for scenarios 3 and 4, the errors are largely within 30% and 100%. Scenario 2 introduces the largest errors, with the retrieved chlorophyll concentration virtually uncorrelated with the true values, implying the backscattering must somehow be related to the trophic state. The results of the study suggested These 3 cases confirmed that while it is the absorption by phytoplankton that in large part decides the accuracy of chlorophyll concentration retrieval, for the success of monitoring of global ocean primary productivity we have to improve our knowledge on particle backscattering.

• Journal of electromagnetic engineering and science
• /
• v.12 no.1
• /
• pp.115-121
• /
• 2012

This paper presents a scattering model and measurements of backscattering coefficients for soybean fields. The polarimetric radar backscatters of a soybean field were measured using the ground-based X-band polarimetric scatterometer in an angular range from $20^{\circ}$ to $60^{\circ}$. The backscattering coefficients were also obtained using the COSMO-SkyMed (Spotlight mode, HH-polarization) from July to October 2010. The backscattering coefficients of the soybean field were computed using the 1st-order radiative transfer model (RTM) with field-measured input parameters. The soybean layer is composed of the stems, branches, leaves, and soybean pods. The stems, branches, and pods are modeled with lossy dielectric cylinders, the leaves are modeled with lossy dielectric disks. The estimated backscattering coefficients agree quite well with the field-measured radar backscattering coefficients.

• The Journal of the Acoustical Society of Korea
• /
• v.29 no.1E
• /
• pp.38-44
• /
• 2010

This paper is based on our comments and proposed amendments to the documents, Annex A, Phantom for determining Maximum Depth of Penetration, and Annex B, Local Dynamic Range Using Acoustical Test Objects 87/400/CDV. IEC 61391-2 Ed. 1.0 200X, prepared by IEC technical Committee 87; Ultrasonics. The documents are concerned with the influence of microstructure of reference target material on the ultrasonic backscattering. Previous works on the attenuation due to backreflection and backscattering of reference target materials are reviewed. The drawback to the use of ungraded stainless steel and metallic materials without microstructural data such as, crystal structure, basic acoustic data of sound velocity and attenuation, grain size, roughness and elastic constants has been discussed. The analysis suggested that the insightful conclusion can be made by differentiating the influence arising from target size and microstructure on the backscattering measurements. The microstructural parameters are associated with physical, geometrical, acoustical and mechanical origins of variation with frequency. Further clarification of such a diverse source mechanisms for ultrasonic backscattering would make the target material and its application for medical diagnosis and therapy simpler and more reliable.

• Korean Journal of Remote Sensing
• /
• v.16 no.2
• /
• pp.109-116
• /
• 2000

This study was carried out to assess the use of RADARSAT data which is C-band with HH polarization for the rice growth monitoring in Korea. Nine time-series data were taken by shallow incidence angle (standard beam mode 5 or 6) during rice growing season. And then, backscattering coefficients ($\sigma$$^{\circ}$) were extracted by calibration process for comparing with rice growth parameters such as plant height, leaf area index(LAI), and fresh and dry biomass. Field experimental data concerned with rice growth were collected 8 times for the ground truth at the study area, Tangjin, Chungnam, Korea. At the beginning of rice growth, backscattering coefficients were ranged from -l6~-l3dB when rice fields were not covered with rice canopy and flooded. At the maximum vegetative stage of rice, backscattering coefficients of the rice field were the highest ranging from -4.4dB~-3.1dB. The temporal variation of backscattering coefficient($\sigma$$^{\circ}$) in rice field was significant in this study. Backscattering coefficient ($\sigma$$^{\circ}$) of rice field was a little bit lower again after heading stage than before. This results show RADARSAT data is promising for rice monitoring.

• Proceedings of the IEEK Conference
• /
• 1999.06a
• /
• pp.211-214
• /
• 1999

Periodical surfaces with the sawtooth profile are studied on their backscattering by the TE plane wave incident. The backscattering is calculated by the mode-matching method. The surfaces are perfect conductor and are covered with dielectric materials to make a flat surface. It is observed that a cover filled with multiple dielectric layers can be used to reduce the backscattering at an arbitrary incident angle.

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

• ETRI Journal
• /
• v.18 no.4
• /
• pp.301-313
• /
• 1997

We have found that in the ballistic electron transport in a ring structure, the junction-backscattering contribution is critical for all the major features of the Aharonov-Bohm-type interference patterns. In particular, by considering the backscattering effect, we present new and clear interpretation about the physical origin of the secondary minima in the electrostatic Aharonov-Bohm effect and that of the h/2e oscillations when both the electric and magnetic potentials are present. We have devised a convenient scheme of expanding the conductance by the junction backscattering amplitude, which enables us to determine most important electron paths among infinitely many paths and to gain insight about their contributions to the interference patterns. Based on the scheme, we have identified various interesting interference phenomena in the ballistic ring structure and found that the backscattering effect plays a critical role in all of them.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.17 no.12 s.115
• /
• pp.1181-1188
• /
• 2006

The radar backscattering coefficients of soil surfaces with various roughness conditions are computed at first in this paper. The roughness parameters for various surface-profile lengths are also obtained. Then, the relationship between the radar backscattering coefficients and the profile length is studied. It was shown that the effect of the profile length is negligible on the backscattering coefficient, even though the roughness parameters vary a lot with the length of the surface profile.