• Korean Journal of Environment and Ecology
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• v.32 no.6
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• pp.686-697
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• 2018

Due to the advance in remote sensing technology, it has become easier to more frequently obtain high resolution imagery to detect delicate changes in an extensive area, particularly including forest which is not readily sub-classified. Time-series analysis on high resolution images requires to collect extensive amount of ground truth data. In this study, the potential of land coverage mapas ground truth data was tested in classifying high-resolution imagery. The study site was Wonju-si at Gangwon-do, South Korea, having a mix of urban and natural areas. KOMPSAT-3A imagery taken on March 2015 and land coverage map published in 2017 were used as source data. Two pixel-based classification algorithms, Support Vector Machine (SVM) and Random Forest (RF), were selected for the analysis. Forest only classification was compared with that of the whole study area except wetland. Confusion matrixes from the classification presented that overall accuracies for both the targets were higher in RF algorithm than in SVM. While the overall accuracy in the forest only analysis by RF algorithm was higher by 18.3% than SVM, in the case of the whole region analysis, the difference was relatively smaller by 5.5%. For the SVM algorithm, adding the Majority analysis process indicated a marginal improvement of about 1% than the normal SVM analysis. It was found that the RF algorithm was more effective to identify the broad-leaved forest within the forest, but for the other classes the SVM algorithm was more effective. As the two pixel-based classification algorithms were tested here, it is expected that future classification will improve the overall accuracy and the reliability by introducing a time-series analysis and an object-based algorithm. It is considered that this approach will contribute to improving a large-scale land planning by providing an effective land classification method on higher spatial and temporal scales.

• Journal of the Korean Association of Geographic Information Studies
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• v.22 no.2
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• pp.36-49
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• 2019

The objectives of this study were to extract "Field Survey Based Infection Tree of Pine Wilt Disease(FSB_ITPWD)" and "Object Classification Based Infection Tree of Pine Wilt Disease(OCB_ITPWD)" from the Research Forest at Kangwon National University, and evaluate the spatial distribution characteristics and occurrence intensity of wood infested by pine wood nematode. It was found that the OCB optimum weights (OCB) were 11 for Scale, 0.1 for Shape, 0.9 for Color, 0.9 for Compactness, and 0.1 for Smoothness. The overall classification accuracy was approximately 94%, and the Kappa coefficient was 0.85, which was very high. OCB_ITPWD area is approximately 2.4ha, which is approximately 0.05% of the total area. When the stand structure, distribution characteristics, and topographic and geographic factors of OCB_ITPWD and those of FSB_ITPWD were compared, age class IV was the most abundant age class in FSB_ITPWD (approximately 55%) and OCB_ITPWD (approximately 44%) - the latter was 11% lower than the former. The diameter at breast heigh (DBH at 1.2m from the ground) results showed that (below 14cm) and (below 28cm) DBH trees were the majority (approximately 93%) in OCB_ITPWD, while medium and (more then 30cm) DBH trees were the majority (approximately 87%) in FSB_ITPWD, indicating different DBH distribution. On the other hand, the elevation distribution rate of OCB_ITPWD was mostly between 401 and 500m (approximately 30%), while that of FSB_ITPWD was mostly between 301 and 400m (approximately 45%). Additionally, the accessibility from the forest road was the highest at "100m or less" for both OCB_ITPWD (24%) and FSB_ITPWD (31%), indicating that more trees were infected when a stand was closer to a forest road with higher accessibility. OCB_ITPWD hotspots were 31 and 32 compartments, and it was highly distributed in areas with a higher age class and a higher DBH class.

• Korean Journal of Remote Sensing
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• v.38 no.5_1
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• pp.609-625
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• 2022

Validation of satellite data products is critical for subsequent analysis that is based on the data. Particularly, performance of ocean color products in turbid and shallow near-land ocean areas has been questioned for long time for its difficulty that stems from the complex optical environment with varying distribution of water constituents. Furthermore, validation with ship-based or station-based measurements has also exhibited clear limitation in its spatial scale that is not compatible with that of satellite data. This study firstly performed validation of major GOCI-II products such as remote sensing reflectance, chlorophyll-a concentration, suspended particulate matter, and colored dissolved organic matter, using the in-situ measurements collected from ship-based field campaign. Secondly, this study also presents preliminary analysis on the use of drone images for product validation. Multispectral images were acquired from a MicaSense RedEdge camera onboard a UAV to compensate for the significant scale difference between the ship-based measurements and the satellite data. Variation of water radiance in terms of camera altitude was analyzed for future application of drone images for validation. Validation conducted with a limited number of samples showed that GOCI-II remote sensing reflectance at 555 nm is overestimated more than 30%, and chlorophyll-a and colored dissolved organic matter products exhibited little correlation with in-situ measurements. Suspended particulate matter showed moderate correlation with in-situ measurements (R²~0.6), with approximately 20% uncertainty.

• Economic and Environmental Geology
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• v.55 no.5
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• pp.551-561
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• 2022

Geophysical exploration methods are very useful for generating high-resolution images of underground structures, and such methods can be applied to investigation of buried cultural properties and for determining their exact locations. In this study, image feature extraction and image segmentation methods were applied to automatically distinguish the structures of buried relics from the high-resolution ground-penetrating radar (GPR) images obtained at the center of Silla Kingdom, Gyeongju, South Korea. The major purpose for image feature extraction analyses is identifying the circular features from building remains and the linear features from ancient roads and fences. Feature extraction is implemented by applying the Canny edge detection and Hough transform algorithms. We applied the Hough transforms to the edge image resulted from the Canny algorithm in order to determine the locations the target features. However, the Hough transform requires different parameter settings for each survey sector. As for image segmentation, we applied the connected element labeling algorithm and object-based image analysis using Orfeo Toolbox (OTB) in QGIS. The connected components labeled image shows the signals associated with the target buried relics are effectively connected and labeled. However, we often find multiple labels are assigned to a single structure on the given GPR data. Object-based image analysis was conducted by using a Large-Scale Mean-Shift (LSMS) image segmentation. In this analysis, a vector layer containing pixel values for each segmented polygon was estimated first and then used to build a train-validation dataset by assigning the polygons to one class associated with the buried relics and another class for the background field. With the Random Forest Classifier, we find that the polygons on the LSMS image segmentation layer can be successfully classified into the polygons of the buried relics and those of the background. Thus, we propose that these automatic classification methods applied to the GPR images of buried cultural heritage in this study can be useful to obtain consistent analyses results for planning excavation processes.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.1
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• pp.83-89
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• 2010

Purpose: The Wide Beam Reconstruction (WBR) algorithms that UltraSPECT, Ltd. (U.S) has provides solutions which improved image resolution by eliminating the effect of the line spread function by collimator and suppression of the noise. It controls the resolution and noise level automatically and yields unsurpassed image quality. The aim of this study is WBR of whole body bone scan in usefulness of clinical application. Materials and Methods: The standard line source and single photon emission computed tomography (SPECT) reconstructed spatial resolution measurements were performed on an INFINA (GE, Milwaukee, WI) gamma camera, equipped with low energy high resolution (LEHR) collimators. The total counts of line source measurements with 200 kcps and 300 kcps. The SPECT phantoms analyzed spatial resolution by the changing matrix size. Also a clinical evaluation study was performed with forty three patients, referred for bone scans. First group altered scan speed with 20 and 30 cm/min and dosage of 740 MBq (20 mCi) of $^{99m}Tc$-HDP administered but second group altered dosage of $^{99m}Tc$-HDP with 740 and 1,110 MBq (20 mCi and 30 mCi) in same scan speed. The acquired data was reconstructed using the typical clinical protocol in use and the WBR protocol. The patient's information was removed and a blind reading was done on each reconstruction method. For each reading, a questionnaire was completed in which the reader was asked to evaluate, on a scale of 1-5 point. Results: The result of planar WBR data improved resolution more than 10%. The Full-Width at Half-Maximum (FWHM) of WBR data improved about 16% (Standard: 8.45, WBR: 7.09). SPECT WBR data improved resolution more than about 50% and evaluate FWHM of WBR data (Standard: 3.52, WBR: 1.65). A clinical evaluation study, there was no statistically significant difference between the two method, which includes improvement of the bone to soft tissue ratio and the image resolution (first group p=0.07, second group p=0.458). Conclusion: The WBR method allows to shorten the acquisition time of bone scans while simultaneously providing improved image quality and to reduce the dosage of radiopharmaceuticals reducing radiation dose. Therefore, the WBR method can be applied to a wide range of clinical applications to provide clinical values as well as image quality.

• Economic and Environmental Geology
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• v.45 no.3
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• pp.277-294
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• 2012

The characteristics of temporal spacial radon variation in soil according to parent rock type and affecting factors were studied in Busan, Korea. The concentration of $^{222}Rn$ in soils and their parent elements ($^{226}Ra$,$^{228}Ra$, U and Th) in rocks and soils were measured at 24 sites in Busan area. The distribution and transportation behavior of these parent elements were analyzed and their correlations to radon concentration in soil were determined. Topographic effects were also evaluated. Two in-situ radon measurement (soil probe and buried tube) methods were applied to measure radon concentration in soil and their accuracies were evaluated. The spatial variation of radon in soil generally reflected U concentration in the parent rock. Average radon concentrations were higher in plutonic rocks than in volcanic rocks and were decreased in the order of felsic>intermediate>mafic rock. However, the radon concentrations were significantly varied in soils developed from same parent rocks due to the disequilibrium of U and $^{226}Ra$ between rock and soil. As results, the correlation of these element concentrations between rocks and soils was very low and radon concentrations in soils had highly co-related to the concentrations of these elements in soils. Th and $^{228}Ra$ show complex enrichment characteristics, differing significantly with U, in soils developed from same parent rock because the geochemical behavior of these elements during weathering and soil developing process was different with U. The radon concentrations in the same depth of soil in slope area were also different according to positions. The radon concentrations in soils developed from same parent rocks (19 sites at Pusan National University) varied 6.8~29.8Bq/L range because of small scale topographic variation. The opposite seasonal variation pattern of radon were observed according to soil properties. It was determined that buried tube method is more accurate method than soil probe method and was very advantageous application for the analysis for the characteristics of temporal spacial radon variation in soil.

• Korean Journal of Environment and Ecology
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• v.34 no.5
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• pp.358-371
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• 2020

As climate change is expected to lead to a severe reduction of biodiversity, studies to investigate the reasons for habitat loss, growth decline, and death of Korean fir (Abies koreana Wilson), endangered alpine/subalpine species in Korea, have been conducted for years but found no clear answer yet. This study reviewed previous studies on Korean fir published in the journals in the past 40 years, 1980 through 2020, into 10-year units, examined the study trend by period, region, and subject with a focus on ecological studies, and analyzed the study results. The ecological studies were categorized into evolutionary ecology, physiological ecology, population ecology, and landscape ecology. Based on the results, we suggested the required research fields in the future. We found a total of 73 papers published in the past 40 years and 48 (65.8%) of them published in the past 10 years. In terms of region, Mt. Halla accounted for the most as 41 papers were on it. In terms of ecological subjects, the physiological ecology accounted for the most with 38, and the evolutionary ecology accounted for the least with 10. The review of the study results showed that many studies identified water stress caused by the water resource imbalance due to temperature increase and spring precipitation reduction following climate change as the main reason for the decline and habitat loss of Korean fir. However, recent studies suggested other factors, such as soil environment, disturbing organisms, and climatic events. The cause of the decline and death of the Korean fir not yet being clearly identified is that most of the studies dealt with the basic content, were carried out intermittently, and were concentrated in some regions. Therefore, we need long-term studies with advanced technology in each study subject at a local scale to find the cause of Korean fir decline and present sustainable management and conservation. Moreover, it is necessary to extend our study subjects to ecosystem ecology and systems ecology to integrate the results from various study subjects for a comprehensive understanding of the reason for Korean fir declines. The results of comprehensive studies could provide clearer answers for Korean fir's declines and the alternatives of conservation management and practices.

• Journal of Korea Water Resources Association
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• v.48 no.7
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• pp.553-566
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• 2015

Acoustic Doppler Current Profilers(ADCPs) have capability to concurrently capitalize three-dimensional velocity vector and bathymetry with highly efficient and rapid manner, and thereby enabling ADCPs to document the hydrodynamic and morphologic data in very high spatial and temporal resolution better than other contemporary instruments. However, ADCPs are also limited in terms of the inevitable unmeasured regions near bottom, surface, and edges of a given cross-section. The velocity in those unmeasured regions are usually extrapolated or assumed for calculating flow discharge, which definitely affects the accuracy in the discharge assessment. This study aimed at scrutinizing a conventional extrapolation method(i.e., the 1/6 power law) for estimating the unmeasured regions to figure out the accuracy in ADCP discharge measurements. For the comparative analysis, we collected spatially dense velocity data using ADV as well as stationary ADCP in a real-scale straight river channel, and applied the 1/6 power law for testing its applicability in conjunction with the logarithmic law which is another representative velocity law. As results, the logarithmic law fitted better with actual velocity measurement than the 1/6 power law. In particular, the 1/6 power law showed a tendency to underestimate the velocity in the near surface region and overestimate in the near bottom region. This finding indicated that the 1/6 power law could be unsatisfactory to follow actual flow regime, thus that resulted discharge estimates in both unmeasured top and bottom region can give rise to discharge bias. Therefore, the logarithmic law should be considered as an alternative especially for the stationary ADCP discharge measurement. In addition, it was found that ADCP should be operated in at least more than 0.6 m of water depth in the left and right edges for better estimate edge discharges. In the future, similar comparative analysis might be required for the moving boat ADCP discharge measurement method, which has been more widely used in the field.

• Economic and Environmental Geology
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• v.51 no.5
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• pp.409-428
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• 2018

Yeongdong area is located on the border zone between Precambrian Yeongnam massif and central southeastern Ogcheon metamorphic belt, in which Cretaceous Yeongdong sedimentary basin exists. Main geology in this area consists of Precambrian Sobaeksan gneiss complex, Mesozoic igneous and sedimentary rocks and Quaternary alluvial deposits. Above this, age-unknown Ogcheon Supergroup, Paleozoic sedimentary rocks and Tertiary granites also occur in small scale in the northwestern part. This study focuses on the link between the various geology and Rn concentrations in groundwater. For this, twenty wells in alluvial/weathered zone and sixty bedrock aquifer wells were used. Groundwater sampling campaigns were twice run at wet season in August 2015 and dry season in March 2016. Some wells placed in alluvial/weathered part of Precambrian metamorphic rocks and Jurassic granite terrains, as well as Cretaceous porphyry, showed elevated Rn concentrations in groundwater. However, detailed geology showed the distinct feature that these high-Rn groundwaters in metamorphic and granitic terrains are definitely related to proximity of aquifer rocks to Cretaceous porphyry in the study area. The deeper wells placed in bedrock aquifer showed that almost the whole groundwaters in biotite gneiss and schist of Sobaeksan gneiss complex and in Cretaceous sedimentary rocks of Yeongdong basin have low level of Rn concentrations. On the other hand, groundwaters occurring in rock types of granitic gneiss or granite gneiss among Sobaeksan gneiss complex have relatively high Rn concentrations. And also, groundwaters occurring in the border zone between Triassic Cheongsan granites and two-mica granites, and in Jurassic granites neighboring Cretaceous porphyry have relatively high Rn concentrations. Therefore, to get probable and meaningful results for the link between Rn concentrations in groundwater and surrounding geology, quite detailed geology including small-scaled dykes or vein zones should be considered. Furthermore, it is necessary to take account of the spatial proximity of well location to igneous rocks associated with some mineralization/hydrothermal alteration zone rather than in-situ geology itself.

• Korean Journal of Ecology and Environment
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• v.39 no.3 s.117
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• pp.352-365
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• 2006

In order to evaluate the change of aquatic environment in the reclaimed Hwaong Reservoir, situated in the early stage after construction, this study was conducted to measure the change of precipitation, temperature, and salinity from June 2002 to January 2006. The range and mean of temperature was $-0.7{\sim}33.4^{\circ}C$ and $13.6^{\circ}C$, respectively. Temperature of upstream part rapidly changed during the transitional period; from spring to summer and from fall to winter. It showed abrupt decrease with high discharge from the streams temporarily. While, hypolimnetic temperature of upstream happened to be somewhat higher than that of surface or downstream. The range and mean of salinity was 0.3${\sim}$32.3 psu and 25.3 psu, respectively. Vertical difference of salinity was marked, and the change in the surface water was much higher than middle or bottom layers. It showed the marked difference at all stations, except for the bottom layer of upstream into which Namyang Stream flows, indicating that vertical gradient of salinity is strongly sustained in the reservoir. Salinity was changed markedly during the storm period (June${\sim}$October), and freshwater with low salinity was expanded from upstream to downstream along the surface layer. The surface of the reservoir was totally covered by the stream discharged water with a large amount of silt and low salinity during this period. The difference of temperature and salinity between the surface and bottom layer ranged $-10.6{\sim}9.7^{\circ}C$ and $-27.1{\sim}30.0$ psu, respectively. The big difference of salinity appeared with a large discharge of freshwater from the streams or large input of seawater through the gate. Salinity was negatively correlated with temperature, indicating the influence of monsoon storm events on the salinity under the whole watershed scale of this brackish reclaimed reservoir.