• Geophysics and Geophysical Exploration
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• v.12 no.3
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• pp.268-277
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• 2009

Recently as the interest in the development of domestic ore deposits has increased, we can easily find some studies on exploration geophysics-based ore deposit survey in literature. Geophysical surveys have been applied to the investigation of both metallic and non-metallic ore deposit. For metallic ore-deposit survey, the 2D electrical resistivity method has been popularly used, because metallic mineral deposits are generally more conductive than surrounding media. However, geological structures are 3D rather than 2D structures, which may lead to misinterpretation in 2D inversion section. In this study, 3D effects are examined for several 3D structures such as a width-varying dyke model and a wedge-shaped model. We also investigate the effects of the direction of survey line. Numerical results show that the width-varying dyke model yields some low resistivity zone in the deep part, which is independent of real ore-body location. For the wedge-shaped model, even though the survey line is located apart from the ore body, the 2D inversion section still shows low resistivity zone in the deep part. When the survey line is not perpendicular to the strike of the ore body, the low resistivity zone is slightly broader but shallower than that obtained along the survey line perpendicular to the strike. For the survey lines that have an angle smaller than $45^{\circ}$ with the strike of the ore body, the inversion results are totally distorted. From these results, we conclude that 2-D survey and interpretation can lead to misinterpretation of subsurface structures, which may be linked to economical loss. Eventually, we recommend to apply 3-D rather than 2-D electrical resistivity survey for ore-deposit survey.

• Journal of the Korean earth science society
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• v.30 no.6
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• pp.699-708
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• 2009

Recently as the interest in the development of domestic ore deposits has increased, we can easily find some studies on exploration geophysics-based ore-deposit survey in literature. Based on the fact that mineralized zone are generally more conductive than surrounding media, electrical resistivity survey among several geophysical surveys has been applied to investigate metallic ore deposits. Most of them are grounded on 2-D survey. However, 2-D inversion may lead to some misinterpretation for 3-D geological structures. In this study, we investigate the feasibility of the 3-D electrical resistivity survey to 3-D vein-type ore deposits. We first simulate 2-D dipole-dipole survey data for survey lines normal to the strike and 3-D pole-pole survey data, and then perform 3-D inversion. For 3-D ore-body structures, we assume a width-varying dyke, a wedge-shaped, and a fault model. The 3-D inversion results are compared to 2-D inversion results. By comparing 3-D inversion results for 2-D dipole-dipole survey data to 3-D inversion results for 3-D pole-pole survey data, we could note that the 2-D dipole-dipole survey data yield better inversion results than the 3-D pole-pole data, which is due to the main characteristic of the pole-pole array. From these results, we are convinced that if we have certain information on the direction of the strike, it would be desirable to apply 2-D dipole-diple survey for the survey lines normal to the strike. However, in most cases, we do not have any information on the direction of the strike, because we already developed the ore deposit with the outcrops and the remaining ore deposits are buried under the surface. In that case, performing 3-D pole-pole electrical resistivity survey would be a reasonable choice to obtain more accurate interpretation on ore body structure in spite of low resolution of pole-pole array.

• Korean Journal of Remote Sensing
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• v.37 no.5_1
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• pp.1135-1147
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• 2021

In order to geometrically correct high-resolution satellite imagery, the sensor modeling process that restores the geometric relationship between the satellite sensor and the ground surface at the image acquisition time is required. In general, high-resolution satellites provide RPC (Rational Polynomial Coefficient) information, but the vendor-provided RPC includes geometric distortion caused by the position and orientation of the satellite sensor. GCP (Ground Control Point) is generally used to correct the RPC errors. The representative method of acquiring GCP is field survey to obtain accurate ground coordinates. However, it is difficult to find the GCP in the satellite image due to the quality of the image, land cover change, relief displacement, etc. By using image maps acquired from various sensors as reference data, it is possible to automate the collection of GCP through the image matching algorithm. In this study, the RPC of KOMPSAT-3A satellite image was corrected through the extracted matching point using the UAV (Unmanned Aerial Vehichle) imagery. We propose a pre-porocessing method for the extraction of matching points between the UAV imagery and KOMPSAT-3A satellite image. To this end, the characteristics of matching points extracted by independently applying the SURF (Speeded-Up Robust Features) and the phase correlation, which are representative feature-based matching method and area-based matching method, respectively, were compared. The RPC adjustment parameters were calculated using the matching points extracted through each algorithm. In order to verify the performance and usability of the proposed method, it was compared with the GCP-based RPC correction result. The GCP-based method showed an improvement of correction accuracy by 2.14 pixels for the sample and 5.43 pixelsfor the line compared to the vendor-provided RPC. In the proposed method using SURF and phase correlation methods, the accuracy of sample was improved by 0.83 pixels and 1.49 pixels, and that of line wasimproved by 4.81 pixels and 5.19 pixels, respectively, compared to the vendor-provided RPC. Through the experimental results, the proposed method using the UAV imagery presented the possibility as an alternative to the GCP-based method for the RPC correction.