• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.8 no.2
• /
• pp.185-196
• /
• 1997

By considering the definition and application of resolution as well as the concept and theory of SAR, the essential contents of the SAR design and analysis are described. This paper is to compare and analyze the resolution performance capability of three techniques for achieving azimuth resolution such as the real aperture, the unfocused and the focused techniques, through the simulation. Simulation is performed to make the restricted conditions for the unfocused technique that can be implemented by the less commputing load of signal processingand the lower cost. Through the mission analysis, the use of SAR image can be applied for estimation of whole situation at the regional area in the field of military demands for tactical purpose as well as civilian demands for the damage of disaster. RPV and sall or medium aircraft are selected to carry the SAR for these purposes and the proper resolution turns ou 5~15 m. The trade-off study of variables through the simulations results in the proper conditions such that range is less 3, 000 m, Wavelength is 1~10 m, and the raw signals and results processed by three techniques for two point targets are exhibited undr such conditions. Therefore, at some points, the result of this paper si proposed for useful applications of unforcused technique in the restricted conditions except the identification of the small target at a long range re- quired for high resolution.

• Korean Journal of Remote Sensing
• /
• v.37 no.5_1
• /
• pp.1215-1227
• /
• 2021

Surface reflectance, as a product of the absolute atmospheric correction process of low-orbit satellite imagery, is the basic data required for accurate vegetation analysis. The Commission on Earth Observation Satellite (CEOS) has conducted research and guidance to produce analysis-ready data (ARD) on surface reflectance products for immediate use by users. However, this trend is still in the early stages of research dealing with ARD for high-resolution multispectral images such as KOMPSAT-3A and CAS-500, as it targets medium- to low-resolution satellite images. This study first summarizes the types of distribution of ARD data according to existing cases. The link between Open Data Cube (ODC), the cloud-based satellite image application platforms, and ARD data was also explained. As a result, we present practical ARD deployment steps for high-resolution satellite images and several types of application models in the conceptual level for high-resolution satellite images deployed in ODC and cloud environments. In addition, data pricing policies, accuracy quality issue, platform applicability, cloud environment issues, and international cooperation regarding the proposed implementation and application model were discussed. International organizations related to Earth observation satellites, such as Group on Earth Observations (GEO) and Committee on Earth Observation Satellites (CEOS), are continuing to develop system technologies and standards for the spread of ARD and ODC, and these achievements are expanding to the private sector. Therefore, a satellite-holder country looking for worldwide markets for satellite images must develop a strategy to respond to this international trend.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.17 no.2
• /
• pp.167-176
• /
• 1999

The study about quantitative or qualitative analysis of object using digital image is being progressed actively with the development of the image medium and image process technique. But, it is very high that the dependency about image acquisition system of high resolution for image analysis of high accuracy and it is a equipment of high-price. In this study, I extracted the optimum condition of image enhancement by analyzing and enhancing the multiple images which were acquired by system of low-price. And I carried out the analysis of 3D accuracy by being applied the optimum condition of image enhancement. In the result of analysis of average 3D positioning error using law image and enhanced image which is acquired by applying the optimum condition of image enhancement, I could obtain the progressed accuracy about 10％ on the enhanced image.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.21 no.6
• /
• pp.1-6
• /
• 1984

This paper describes that the compensation of frequency dependent attenuation (F.D.A.) and faithful envelope detection using the analytic signal magnitude (A.S.M.) improve the range resolut ion in an acoustic medium. It is shown that a mean of computing the magnitude of. analytic signal is better than that of conventional A-mode. In addition, this proposed method is much easier than the above methods to detect two closely spaced interfaces on the A-mode. As the result of experiment, we obtained range resolution of 0.5 mm with transducer of 3.5 MHz. This method can be applied to medical experiment, diagonostic and nondestructive testing.

• Water Engineering Research
• /
• v.6 no.2
• /
• pp.73-89
• /
• 2005

Two kinds of high resolution GCMs with the same spatial resolutions but with different schemes run by domestic and foreign agencies are used to clarify the usefulness and sensitivity of GCM for water resources applications for Korea. One is AMIP-II (Atmospheric Model Intercomparison Project-II) type GCM simulation results done by ECMWF (European Centre for Medium-Range Weather Forecasts) and the other one is AMIP-I type GCM simulation results done by METRI (Korean Meteorological Research Institute). Observed mean areal precipitation, temperature, and discharge values on 7 major river basins were used for target variables. Monte Carlo simulation was used to establish the significance of the estimator values. Sensitivity analyses were done in accordance with the proposed ways. Through the various tests, discrimination condition is sensitive for the distribution of the data. Window size is sensitive for the data variation and the area of the basins. Discrimination abilities of each nodal value affects on the correct association. In addition to theses sensitivity analyses results, we also noticed some characteristics of each GCM. For Korean water resources, monthly and small window setting analyses are recommended using GCMs.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2010.04a
• /
• pp.277-280
• /
• 2010

There is a need to convert the old low- or medium-resolution satellite image-based thematic mapping to the high-resolution satellite image-based mapping of GSD 1m grade or lower. There is also a need to generate middle- or large-scale thematic maps of 1:5,000 or lower. In this study, the DEM and orthoimage is generated with the KOMPSAT-2 stereo image of Yuseong-gu, Daejeon Metropolitan City. By utilizing the orthoimage, automatic extraction experiments of land cover information are generated for buildings, roads and urban areas, raw land(agricultural land), mountains and forests, hydrosphere, grassland, and shadow. The experiment results show that it is possible to classify, in detail, for natural features such as the hydrosphere, mountains and forests, grassland, shadow, and raw land. While artificial features such as roads, buildings, and urban areas can be easily classified with automatic extraction, there are difficulties on detailed classifications along the boundaries. Further research should be performed on the automation methods using the conventional thematic maps and all sorts of geo-spatial information and mapping techniques in order to classify thematic information in detail.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2007.06a
• /
• pp.139-144
• /
• 2007

To delineate subglacial and englacial images of the western Fourcade Glacier in Antarctica, GPR data were acquired along a 470 m profile in November 2006. Signature deconvolution, migration velocity analysis, and finite difference depth migration were effective in increasing vertical resolution, obtaining the velocity function, and yielding clear depth images of the mixed-phase single-channel data, respectively. The source signature was extracted through stacking reflection signals from the basement. The deconvolution successfully compressed the source signatures to increase temporal resolution and attenuated reverberations. Medium velocities were analyzed with 112 diffraction events by the constant-velocity migration method based on the Stolt algorithm. Finally, depth migration based on the finite difference algorithm provided clear englacial and subglacial images in the laterally-varying velocity field.

• ETRI Journal
• /
• v.27 no.4
• /
• pp.385-393
• /
• 2005

This paper presents an application of digital signal processing to data acquired by the radio imaging method (RIM) that was adopted to measure moisture distribution inside the human body. RIM was originally developed for the mining industry; we are applying the method to a biomedical measurement because of its simplicity, economy, and safety. When a two-dimensional image was constructed from the measured data, the method provided insufficient resolution because the wavelength of the measurement medium, a weak electromagnetic wave in a VHF band, was longer than human tissues. We built and measured a phantom, a model simulating the human body, consisting of two water tanks representing large internal organs. A digital equalizer was applied to the measured values as a weight function, and images were reconstructed that corresponded to the original shape of the two water tanks. As a result, a two-dimensional image containing two individual peaks corresponding to the original two small water tanks was constructed. The result suggests the method was applicable to biomedical measurement by the assistance of digital signal processing. This technique may be applicable to home-based medical care and other situations in which safety, simplicity, and economy are important.

• Wind and Structures
• /
• v.24 no.3
• /
• pp.223-247
• /
• 2017

By using numerical simulation, vast and detailed information and observation of the physics of flow over a train model can be obtained. However, the accuracy of the numerical results is questionable as it is affected by grid convergence error. This paper describes a systematic method of computational grid refinement for the Unsteady Reynolds Navier-Stokes (URANS) of flow around a generic model of trains using the OpenFOAM software. The sensitivity of the computed flow field on different mesh resolutions is investigated in this paper. This involves solutions on three different grid refinements, namely fine, medium, and coarse grids to investigate the effect of grid dependency. The level of grid independence is evaluated using a form of Richardson extrapolation and Grid Convergence Index (GCI). This is done by comparing the GCI results of various parameters between different levels of mesh resolutions. In this study, monotonic convergence criteria were achieved, indicating that the grid convergence error was progressively reduced. The fine grid resolution's GCI value was less than 1%. The results from a simulation of the finest grid resolution, which includes pressure coefficient, drag coefficient and flow visualization, are presented and compared to previous available data.

• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.1
• /
• pp.34.1-34.1
• /
• 2011

Combining a detailed non-grey radiative transfer computation with the three dimensional hydrodynamics, we investigate a reliable numerical scheme for turbulent convection in the solar surface. The solar photosphere is the extremely turbulent region composed of partly ionized compressible gases in high temperature. Especially, the super adiabatic layer (SAL) near the solar photosphere is the shallow transition region where the energy transport varies steeply from convection to radiation. In order to describe physical processes accurately, a detailed treatment of radiative transfer should be considered as well as the high resolution computation of fluid dynamics. For a direct computation of radiation fields, the Accelerated Lambda Iteration (ALI) methods have been applied to hydrodynamical medium, incorporating the Opacity Distribution Function (ODF) as a realistic schemes for non-grey problems. Computational domain is the rectangular box of dimensions $42{\times}3Mn$ with the resolution of $1202{\times}190$ meshed grids, which covers several granules horizontally and 8 ~ 9 pressure scale heights vertically. During several convective turn-over times, the 3-D snapshots have been compiled with a second order accuracy. In addition, our radiation-hydrodynamical computation has been compared with the classical approximations such as grey atmospheres and Eddington approximation.