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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Korean Journal of Remote Sensing
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Journal DOI :
The Korean Society of Remote Sensing
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Volume & Issues
Volume 31, Issue 6 - Dec 2015
Volume 31, Issue 5 - Oct 2015
Volume 31, Issue 4 - Aug 2015
Volume 31, Issue 3 - Jun 2015
Volume 31, Issue 2 - Apr 2015
Volume 31, Issue 1 - Feb 2015
Selecting the target year
Near-Infrared Spectral Characteristics in Presence of Sun Glint Using CASI-1500 Data in Shallow Waters
Jeon, Joo-Young ; Kim, Sun-Hwa ; Yang, Chan-Su ;
Korean Journal of Remote Sensing, volume 31, issue 4, 2015, Pages 281~291
DOI : 10.7780/kjrs.2015.31.4.1
Sun glint correction methods of hyperspectral data that have been developed so far have not considered the various situations and are often adequate for only certain conditions. Also there is an inaccurate assumption that the signal in NIR wavelength is zero. Therefore, this study attempts to analyze the NIR spectral properties of sun glint effect in coastal waters. For the analysis, CASI-1500 airborne hyperspectral data, bathymetry data and in-situ data obtained at coastal area near Sin-Cheon, Jeju Island, South Korea were used. The spectral characteristics of radiance and reflectance at the five NIR wavelengths (744 nm, 758 nm, 772 nm, 786 nm, and 801 nm) are analyzed by using various statistics, spatial and spectral variation of sun-glinted area under conditions of the bottom types of benthos, barren rocks and sand with similar water depth. Through the quantitative analysis, we found that the relation of water depth or bottom type with sun glint is relatively less which is a similar result with the previous studies. However the sun glint are distributed similarly with the patterns of the direction of wave propagation. It is confirmed that the areas with changed direction of wave propagation were not affected by the sun glint. The spatial and spectral variations of radiance and reflectance are mainly caused by the effect of sun glint and waves. The radiance or reflectance of more sun-glinted areas are increased approximately 1.5 times and the standard deviations are also increased three times compared to the less sun glinted areas. Through this study, the further studies of sun glint correction method in coastal water using the patterns of wave propagation and diffraction will be placed.
Extraction of water body in before and after images of flood using Mahalanobis distance-based spectral analysis
Ye, Chul-Soo ;
Korean Journal of Remote Sensing, volume 31, issue 4, 2015, Pages 293~302
DOI : 10.7780/kjrs.2015.31.4.2
Water body extraction is significant for flood disaster monitoring using satellite imagery. Conventional methods have focused on finding an index, which highlights water body and suppresses non-water body such as vegetation or soil area. The Normalized Difference Water Index (NDWI) is typically used to extract water body from satellite images. The drawback of NDWI, however, is that some man-made objects in built-up areas have NDWI values similar to water body. The objective of this paper is to propose a new method that could extract correctly water body with built-up areas in before and after images of flood. We first create a two-element feature vector consisting of NDWI and a Near InfRared band (NIR) and then select a training site on water body area. After computing the mean vector and the covariance matrix of the training site, we classify each pixel into water body based on Mahalanobis distance. We also register before and after images of flood using outlier removal and triangulation-based local transformation. We finally create a change map by combining the before-flooding water body and after-flooding water body. The experimental results show that the overall accuracy and Kappa coefficient of the proposed method were 97.25% and 94.14%, respectively, while those of the NDWI method were 89.5% and 69.6%, respectively.
Measurements of Impervious Surfaces - per-pixel, sub-pixel, and object-oriented classification -
Kang, Min Jo ; Mesev, Victor ; Kim, Won Kyung ;
Korean Journal of Remote Sensing, volume 31, issue 4, 2015, Pages 303~319
DOI : 10.7780/kjrs.2015.31.4.3
The objectives of this paper are to measure surface imperviousness using three different classification methods: per-pixel, sub-pixel, and object-oriented classification. They are tested on high-spatial resolution QuickBird data at 2.4 meters (four spectral bands and three principal component bands) as well as a medium-spatial resolution Landsat TM image at 30 meters. To measure impervious surfaces, we selected 30 sample sites with different land uses and residential densities across image representing the city of Phoenix, Arizona, USA. For per-pixel an unsupervised classification is first conducted to provide prior knowledge on the possible candidate spectral classes, and then a supervised classification is performed using the maximum-likelihood rule. For sub-pixel classification, a Linear Spectral Mixture Analysis (LSMA) is used to disentangle land cover information from mixed pixels. For object-oriented classification several different sets of scale parameters and expert decision rules are implemented, including a nearest neighbor classifier. The results from these three methods show that the object-oriented approach (accuracy of 91%) provides more accurate results than those achieved by per-pixel algorithm (accuracy of 67% and 83% using Landsat TM and QuickBird, respectively). It is also clear that sub-pixel algorithm gives more accurate results (accuracy of 87%) in case of intensive and dense urban areas using medium-resolution imagery.
Atmospheric Correction Problems with Multi-Temporal High Spatial Resolution Images from Different Satellite Sensors
Lee, Hwa-Seon ; Lee, Kyu-Sung ;
Korean Journal of Remote Sensing, volume 31, issue 4, 2015, Pages 321~330
DOI : 10.7780/kjrs.2015.31.4.4
Atmospheric correction is an essential part in time-series analysis on biophysical parameters of surface features. In this study, we tried to examine possible problems in atmospheric correction of multitemporal High Spatial Resolution (HSR) images obtained from two different sensor systems. Three KOMPSAT-2 and two IKONOS-2 multispectral images were used. Three atmospheric correction methods were applied to derive surface reflectance: (1) Radiative Transfer (RT) - based absolute atmospheric correction method, (2) the Dark Object Subtraction (DOS) method, and (3) the Cosine Of the Uun zeniTh angle (COST) method. Atmospheric correction results were evaluated by comparing spectral reflectance values extracted from invariant targets and vegetation cover types. In overall, multi-temporal reflectance from five images obtained from January to December did not show consistent pattern in invariant targets and did not follow a typical profile of vegetation growth in forests and rice field. The multi-temporal reflectance values were different by sensor type and atmospheric correction methods. The inconsistent atmospheric correction results from these multi-temporal HSR images may be explained by several factors including unstable radiometric calibration coefficients for each sensor and wide range of sun and sensor geometry with the off-nadir viewing HSR images.
An Application of a Sunshine Duration Model Based on GIS Data to Suitability of Measurement Site around the Seonleung Park
Kim, Eun-Ryoung ; Kim, Jae-Jin ;
Korean Journal of Remote Sensing, volume 31, issue 4, 2015, Pages 331~336
DOI : 10.7780/kjrs.2015.31.4.5
In this study, a numerical model developed for sunshine duration based on GIS data was used. This model considers blocking caused by topography and buildings and it is properly applicable to evaluation of sunshine duration environment in urban areas. The model reasonably well predicted the solar altitude and azimuth angels, compared to those provided by Korea Astronomy and Space Science Institute (KASI). The developed model was applied to evaluation of sunshine duration environment around the Seonleung Park located near a building-congested area in Seoul. The model well reproduced shadow caused by buildings and/or topography in the numerical domain at 09:00 on August 1, 2015. In addition, the model was applied to finding a suitable measurement sites for pyrheliometer around the Seonleung Park. The model was also usefully applied to finding a suitable site for pyrheliometer in an urban area.
Water body extraction in SAR image using water body texture index
Ye, Chul-Soo ;
Korean Journal of Remote Sensing, volume 31, issue 4, 2015, Pages 337~346
DOI : 10.7780/kjrs.2015.31.4.6
Water body extraction based on backscatter information is an essential process to analyze floodaffected areas from Synthetic Aperture Radar (SAR) image. Water body in SAR image tends to have low backscatter values due to homogeneous surface of water, while non-water body has higher backscatter values than water body. Non-water body, however, may also have low backscatter values in high resolution SAR image such as Kompsat-5 image, depending on surface characteristic of the ground. The objective of this paper is to present a method to increase backscatter contrast between water body and non-water body and also to remove efficiently misclassified pixels beyond true water body area. We create an entropy image using a Gray Level Co-occurrence Matrix (GLCM) and classify the entropy image into water body and non-water body pixels by thresholding of the entropy image. In order to reduce the effect of threshold value, we also propose Water Body Texture Index (WBTI), which measures simultaneously the occurrence of repeated water body pixel pair and the uniformity of water body in the binary entropy image. The proposed method produced high overall accuracy of 99.00% and Kappa coefficient of 90.38% in water body extraction using Kompsat-5 image. The accuracy analysis indicates that the proposed WBTI method is less affected by the choice of threshold value and successfully maintains high overall accuracy and Kappa coefficient in wide threshold range.
Relationship between sea ice concentration and sea ice albedo over Antarctica
Seo, Minji ; Lee, Chang Suk ; Kim, Hyunji ; Huh, Morang ; Han, Kyung-Soo ;
Korean Journal of Remote Sensing, volume 31, issue 4, 2015, Pages 347~351
DOI : 10.7780/kjrs.2015.31.4.7
Sea ice is a key parameter for understanding the climate change in cryosphere. In this study, we investigated the correlation with the factors that influenced change of the sea ice extent. We used the Sea Ice Concentration (SIC) from Ocean and Sea Ice Satellite Application Facility (OSI-SAF), and surface albedo provided by The Satellite Application Facility on Climate Monitoring (CM SAF). We converted the same temporal and spatial resolution of the data and detected the sea ice using SIC data. We performed the relationship analysis between SIC and sea ice albedo. As a result, we found they have a strong positive correlation. We performed the linear regression between SIC and sea ice albedo, and found they have high-level coefficient of determination. It shows using either SIC or sea ice albedo is possible to estimate the sea ice products.
Improvement of Earth Gravity Field Maps after Pre-processing Upgrade of the GRACE Satellite`s Star Trackers
Ko, Ung-Dai ; Wang, Furun ; Eanes, Richard J. ;
Korean Journal of Remote Sensing, volume 31, issue 4, 2015, Pages 353~360
DOI : 10.7780/kjrs.2015.31.4.8
Earth`s gravity field recovery was improved after the pre-processing upgrade of the Gravity Recovery And Climate Experiments (GRACE) satellite`s star trackers. The star tracker measurements were filtered with a tighter low-pass filtering of 0.025Hz cutoff frequency, instead of a nominal filtering of 0.1Hz cutoff frequency. In addition, a jump removal algorithm was applied to remove discontinuities, due to direct Sun and/or Moon interventions, in the star tracker measurements. During the K-Band Ranging (KBR) calibration maneuvers, large attitude variations could be detected concurrently by both of the star trackers and the accelerometer. The misalignment angles of star trackers between the true frame and the normal frame could be determined by comparing measurements from these sensors. In this paper, new Earth` gravity field maps were obtained using above improvement. Based on comparisons to nominal Earth`s gravity field maps, the new Earth`s gravity field maps were found better than the nominal ones. Among the applied methods, the misalignment calibration of the star trackers had a major impact on the improvement of the new Earth`s gravity field maps.