• Korean Journal of Remote Sensing
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• v.37 no.3
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• pp.475-491
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• 2021

With the recent increase in available high-resolution (< ~1 m) satellite SAR images, the demand for precise registration of SAR images is increasing in various fields including change detection. The registration between high-resolution SAR images acquired in different look angle is difficult due to speckle noise and geometric distortion caused by the characteristics of SAR images. In this study, registration is performed in two stages, coarse and fine, using the x-band SAR data imaged at staring spotlight mode of TerraSAR-X. For the coarse registration, a method combining the adaptive sampling method and SAR-SIFT (Scale Invariant Feature Transform) is applied, and three rigid methods (NCC: Normalized Cross Correlation, Phase Congruency-NCC, MI: Mutual Information) and one non-rigid (Gefolki: Geoscience extended Flow Optical Flow Lucas-Kanade Iterative), for the fine registration stage, was performed for performance comparison. The results were compared by using RMSE (Root Mean Square Error) and FSIM (Feature Similarity) index, and all rigid models showed poor results in all image combinations. It is confirmed that the rigid models have a large registration error in the rugged terrain area. As a result of applying the Gefolki algorithm, it was confirmed that the RMSE of Gefolki showed the best result as a 1~3 pixels, and the FSIM index also obtained a higher value than 0.02~0.03 compared to other rigid methods. It was confirmed that the mis-registration due to terrain effect could be sufficiently reduced by the Gefolki algorithm.

• Journal of Soil and Groundwater Environment
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• v.17 no.5
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• pp.56-67
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• 2012

In the present study, an enhanced subsurface prediction algorithm based on a non-parametric geostatistical model and a history matching technique through Gibbs sampler is developed and the iterative prediction improvement procedure is proposed. The developed model is applied to a simple two-dimensional synthetic case where domain is composed of three different hydrogeologic media with $500m{\times}40m$ scale. In the application, it is assumed that there are 4 independent pumping tests performed at different vertical interval and the history curves are acquired through numerical modeling. With two hypothetical borehole information and pumping test data, the proposed prediction model is applied iteratively and continuous improvements of the predictions with reduced uncertainties of the media distribution are observed. From the results and the qualitative/quantitative analysis, it is concluded that the proposed model is good for the subsurface prediction improvements where the history data is available as a supportive information. Once the proposed model be a matured technique, it is believed that the model can be applied to many groundwater, geothermal, gas and oil problems with conventional fluid flow simulators. However, the overall development is still in its preliminary step and further considerations needs to be incorporated to be a viable and practical prediction technique including multi-dimensional verifications, global optimization, etc. which have not been resolved in the present study.

• Journal of Korea Society of Industrial Information Systems
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• v.22 no.4
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• pp.1-9
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• 2017

In this Paper, Double Encryption Technology Based on Phase-Shifting Digital Holography and Digital Watermarking is Proposed. For the Purpose, we First Set a Logo Image to be used for Digital Watermark and Design a Binary Phase Computer Generated Hologram for this Logo Image using an Iterative Algorithm. And Random Generated Binary Phase Mask to be set as a Watermark and Key Image is Obtained through XOR Operation between Binary Phase CGH and Random Binary Phase Mask. Object Image is Phase Modulated to be a Constant Amplitude and Multiplied with Binary Phase Mask to Generate Object Wave. This Object Wave can be said to be a First Encrypted Image Having a Pattern Similar to the Noise Including the Watermark Information. Finally, we Interfere the First Encrypted Image with Reference Wave using 2-step PSDH and get a Good Visible Interference Pattern to be Called Second Encrypted Image. The Decryption Process is Proceeded with Fresnel Transform and Inverse Process of First Encryption Process After Appropriate Arithmetic Operation with Two Encrypted Images. The Proposed Encryption and Decryption Process is Confirmed through the Computer Simulations.