• Korean Journal of Remote Sensing
• /
• v.36 no.5_3
• /
• pp.1125-1137
• /
• 2020

This study aimed to propose the method of linking satellite image-based forest fire data to supplement the limitation of forest fire survey data that records only the ignition location and area of forest fire. For this purpose, a method was derived to link the fire survey data provided by the Korea Forest Service between January 2012 and December 2019 with MODIS and VIIRS image-based forest fire data. As a result, MODIS and VIIRS-based forest fire data out of 191 wildfires in the forest fire survey data were able to identify 11% and 44% of fire damage area, respectively. An average of 56% of forest damage area was extracted from VIIRS-based forest fire data compared to forest fire areas identified by high-resolution Sentinel-2A satellites. Therefore, for large-scale forest fires, VIIRS wildfire data can be used to compensate for the limitations of forest fire survey data that records only the ignition location and area.

• Korean Journal of Remote Sensing
• /
• v.36 no.4
• /
• pp.535-544
• /
• 2020

In synthetic aperture radar (SAR) based ship detection application, false alarms frequently occur due to various noises caused by the radar imaging process. Among them, radio frequency interference (RFI) and azimuth smearing produce substantial false alarms; the latter also yields longer length estimation of ships than the true length. These two noises are prominent at cross-polarization and relatively weak at co-polarization. However, in general, the cross-polarization data are suitable for ship detection, because the radar backscatter from background sea surface is much less in comparison with the co-polarization backscatter, i.e., higher ship-sea image contrast. In order to improve the ship detection accuracy further, the RFI and azimuth smearing need to be mitigated. In the present letter, Sentinel-1 VV- and VH-polarization intensity data are used to show a novel technique of removing these noises. In this method, median image intensities of noises and background sea surface are calculated to yield arithmetic tendency. A band-math formula is then designed to replace the intensities of noise pixels in VH-polarization with adjusted VV-polarization intensity pixels that are less affected by the noises. To verify the proposed method, the adaptive threshold method (ATM) with a sliding window was used for ship detection, and the results showed that the 74.39% of RFI false alarms are removed and 92.27% false alarms of azimuth smearing are removed.

• Archives of Plastic Surgery
• /
• v.47 no.1
• /
• pp.42-48
• /
• 2020

Background Methods for identifying local lymph node metastasis in malignant melanoma include sentinel lymph node biopsy (SLNB) and lymph node dissection (LND). In particular, SLNB has been widely used in recent years. This study aimed to retrospectively confirm the adequacy of the current indication criteria for SLNB by applying those criteria to a mixed group of patients who previously received SLNB and LND. Methods This study included 77 patients with malignant melanoma of the extremities and trunk who were monitored for >24 months. The patients were classified according to whether the current indication criteria for SLNB were applicable. The sentinel lymph nodes were evaluated for each group. Patients for whom the indication criteria for SLNB and LND were applicable were analyzed according to whether SLNB or LND was performed. Finally, the outpatient records of these patients were reviewed to evaluate recurrence, metastasis, and prognosis. Results Of the 77 patients, SLNB was indicated according to the current criteria in 60 cases. Among the 60 patients for whom SLNB was indicated, 35 survived the follow-up period disease-free, 21 died during the follow-up period, and four experienced metastasis. The 17 patients for whom SLNB was not indicated had no recurrence or metastasis. Conclusions Patients for whom SLNB was not indicated had no recurrence or metastasis. In cases where SLNB is indicated, the possibility of metastasis and recurrence may be high even if SLNB is negative or LND is performed, so more aggressive treatment and careful follow-up are crucial.

• Archives of Reconstructive Microsurgery
• /
• v.19 no.2
• /
• pp.81-87
• /
• 2010

In surgical treatment of the malignant melanoma, radical resection and a sentinel lymph node biopsy are essential procedures to eradicate the tumor and to minimize the risk of local recurrence. For the reconstruction of skin defect after tumor resection, a skin graft has been generally performed procedure. However, if tendon or bone is exposed after tumor resection, simple skin graft is not enough for the coverage of the defect and additional procedure is mandatory. In this study, we reviewed the clinical results of 16 patients, who had been diagnosed with malignant melanoma of the limb and underwent surgical resection and reconstruction of the defect with various methods. The sentinel lymph node dissection was performed in all patients combined with radical excision of the tumor. In 11 cases of positive sentinel lymph nodes, further elective lymph node dissections were performed. The mean tumor invasion depth was 4.54 mm (2~10 mm), and AJCC stage II was most common (9 cases). The pedicled flaps were performed in 10 cases for the reconstruction of defects. All flaps were successfully survived without significant complications until the last follow up. In conclusion, a pedicled flap coverage is very useful reconstruction strategy for the soft tissue defects after radical resection of malignant melanoma.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2018.05a
• /
• pp.148-148
• /
• 2018

Land subsidence caused by excessive groundwater pumping is a serious hydro-geological hazard. The spatial variability in land use, unbalanced groundwater extraction and aquifer characteristics are the key factors which make the problem more difficult to monitor using conventional methods. This study uses the European Space Agency (ESA) Sentinel satellites to investigate and monitor land subsidence varying with different land covers and groundwater use in the arid Quetta valley, Pakistan. The Persistent Scattering Differential Interferometry of Synthetic Aperture Radar (PS-DInSAR) method was used to develop 28 subsidence interferograms of the study area for the period between 16 Oct 2014 and 06 Oct 2016 using ESA's Sentinel-1 SAR data. The uncertainty of DInSAR result is first minimized by removing the dynamic effect caused by atmospheric factors and then filtered using the radar Amplitude Dispersion Index (ADI) to select only the stable pixels. Finally the subsidence maps were generated by spatially interpolating the land subsidence at the stable pixels, the comparison of DInSAR subsidence with GPS readings showed an R 2 of 0.94 and mean absolute error of $5.7{\pm}4.1mm$. The subsidence maps were also analysed for the effect of aquifer type and 4 land covers which were derived from Sentienl-2 multispectral images. The analysis show that during the two year period, the study area experienced highly non-linear land subsidence ranging from 10 to 280 mm. The subsidence at different land covers was significantly different from each other except between the urban and barren land. The barren land and seasonally cultivated area show minor to moderate subsidence while the orchard and urban area with high groundwater extraction rate showed excessive amount of land subsidence. Moreover, the land subsidence and groundwater drawdown was found to be linearly proportional to each other.

• Korean Journal of Remote Sensing
• /
• v.37 no.6_1
• /
• pp.1625-1630
• /
• 2021

In Bangkok, Thailand, there is an increasing concern for ground subsidence with the rapid urbanization. Given the presence of flood vulnerability due to the flat low-lying topography and proximity to the river delta, it is particularly significant to monitor deformation that can potentially augment flood hazards. In this paper, we have applied persistent scatterer interferometric synthetic aperture radar (PSInSAR) technique to investigate subsidence in Bangkok with the use of Sentinel-1 acquisitions spanning from June 2018 to October 2021. The vertical displacement velocity obtained from both ascending and descending orbits revealed regional-scale subsidence at rates up to 30 mm/yr. In addition, ongoing subsidence was observed in the suburb areas with the localized vertical subsidence exceeding 80 mm. The areas are primarily industrial and agricultural sectors, thus, the ground subsidence detected is probably caused by groundwater withdrawal. However, further work is needed to diagnose the trends of aquifer resources.

• Korean Journal of Remote Sensing
• /
• v.35 no.4
• /
• pp.517-534
• /
• 2019

In abrupt fire disturbances, high quality images suitable for wildfire damage assessment can be difficult to acquire. Quantifying wildfire burn area and severity are essential measures for quick short-term disaster response and efficient long-term disaster restoration. Planetscope (PS) imagery offers 3 m spatial and daily temporal resolution, which can overcome the spatio-temporal resolution tradeoff of conventional satellites, albeit at the cost of spectral resolution. This study investigated the potential of augmenting PS imagery by integrating the spectral information from Sentinel-2 (S2) differenced Normalized Burn Ratio (dNBR) to PS differenced Normalized Difference Vegetation Index (dNDVI) using histogram matching,specifically for wildfire burn area and severity assessment of the Okgye wildfire which occurred on April 4th, 2019. Due to the difficulty in acquiring reference data, the results of the study were compared to the wildfire burn area reported by Ministry of the Interior and Safety. The burn area estimates from this study demonstrated that the histogram-matched (HM) PS dNDVI image produced more accurate burn area estimates and more descriptive burn severity intervals in contrast to conventional methods using S2. The HM PS dNDVI image returned an error of only 0.691% whereas the S2 dNDVI and dNBR images overestimated the wildfire burn area by 5.32% and 106%, respectively. These improvements using PS were largely due to the higher spatial resolution, allowing for the detection of sparsely distributed patches of land and narrow roads, which were indistinguishable using S2 dNBR. In addition, the integration of spectral information from S2 in the PS image resolved saturation effects in areas of low and high burn severity.

• Archives of Plastic Surgery
• /
• v.46 no.5
• /
• pp.441-448
• /
• 2019

Background Merkel cell carcinoma (MCC) is a rare neuroendocrine malignancy affecting the skin, for which timely diagnosis and aggressive treatment are essential. MCC has most often been reported in Caucasians, and case reports in Asians are rare. This study presents our experiences with the surgical treatment and radiotherapy of MCC in Asian patients. Methods We retrospectively reviewed the records of seven MCC patients between 2000 and 2018 from a single institution, and analyzed patient characteristics, tumor characteristics, surgical treatment, sentinel lymph node evaluation, reconstruction, adjuvant radiation therapy, and prognosis. Results Eight MCC lesions occurred in seven patients, most commonly in the head and neck region. All patients underwent surgical excision with reconstruction. The final surgical margin was 1.0 cm in most cases, and reconstruction was most commonly performed with a splitthickness skin graft. Five patients received adjuvant radiotherapy, and two patients received sentinel lymph node biopsy. During the follow-up period, three patients remained well, two died from other causes, one experienced recurrence, and one was lost to follow-up. Conclusions We treated seven Asian MCC patients and our series confirmed that MCC is a very dangerous cancer in Asians as well. Based on our experiences, thorough surgical excision of MCC with histopathological clearance should be considered, with sentinel lymph node evaluation if necessary, followed by appropriate reconstruction and careful postoperative observation. Adjuvant radiation therapy is also recommended for all Asian MCC patients. The results of this case series may provide guidance for the treatment of Asian MCC patients in the future.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.64 no.1
• /
• pp.51-63
• /
• 2022

Up-to-date statistics of crop cultivation status is essential for farm land management planning and the advancement in remote sensing technology allows for rapid update of farming information. The objective of this study was to develop a classification model of rice paddy or winter crop fields based on NDWI, NDVI, and HSV indices using Sentinel-2 satellite images. The 18 locations in central Korea were selected as target areas and photographed once for each during summer and winter with a eBee drone to identify ground truth crop cultivation. The NDWI was used to classify summer paddy fields, while the NDVI and HSV were used and compared in identification of winter crop cultivation areas. The summer paddy field classification with the criteria of -0.195

• Korean Journal of Remote Sensing
• /
• v.38 no.6_4
• /
• pp.1911-1923
• /
• 2022

The availability of high-resolution satellite images provides precise information without direct observation of the research target. Korea Multi-Purpose Satellite (KOMPSAT), also known as the Arirang satellite, has been developed and utilized for earth observation. The machine learning model was continuously proven as a good classifier in classifying remotely sensed images. This study aimed to compare the performance of the support vector machine (SVM) model in classifying the land cover of the Delaware River port area on high and medium-resolution images. Three optical images, which are KOMPSAT-2, KOMPSAT-3A, and Sentinel-2B, were classified into six land cover classes, including water, road, vegetation, building, vacant, and shadow. The KOMPSAT images are provided by Korea Aerospace Research Institute (KARI), and the Sentinel-2B image was provided by the European Space Agency (ESA). The training samples were manually digitized for each land cover class and considered the reference image. The predicted images were compared to the actual data to obtain the accuracy assessment using a confusion matrix analysis. In addition, the time-consuming training and classifying were recorded to evaluate the model performance. The results showed that the KOMPSAT-3A image has the highest overall accuracy and followed by KOMPSAT-2 and Sentinel-2B results. On the contrary, the model took a long time to classify the higher-resolution image compared to the lower resolution. For that reason, we can conclude that the SVM model performed better in the higher resolution image with the consequence of the longer time-consuming training and classifying data. Thus, this finding might provide consideration for related researchers when selecting satellite imagery for effective and accurate image classification.