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Seoul, South Korea
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Lee S.,Pukyong National University | Kim J.,ZEN21 | Jin C.,Korea Aerospace Research Institute | Bae S.,Pukyong National University | Choi C.,Pukyong National University
Instrumentation Science and Technology | Year: 2012

Many countries are increasing their research on monitoring technology to identify and systematically manage various domestic changes. In particular, the need for remote monitoring is increasing in response to climatic disasters, such as flooding, storms, and rising tides caused by global warming. We developed a smartphone-based environmental monitoring system that enables remote monitoring in any place and at any time. The overall system is composed of a 24-hour smartphone-based imaging system, a monitoring information management system to receive the monitoring information, and stereo image rectification software that provides lens distortion correction, geometric correction, and stereo matching of the monitoring images. The system was developed using the Samsung Galaxy S with the Android OS, as well as open source-based software and other hardware. It is easy to install, control remotely, and monitor the status of imaging devices. We assessed the accuracy of the micro-electro-mechanical system (MEMS) sensors of the smartphone to evaluate the applicability of our environmental monitoring system. The assessment was conducted via survey using metric cameras, a global positioning system receiver, a three-dimensional laser scanner and total station, geometric correction, and digital elevation models generated with camera internal elements, external elements, and ground control points. We demonstrated the effectiveness of the system, and showed that the accuracy of the MEMS sensor and camera calibration have a significant effect on image analysis. © 2012 Taylor and Francis Group, LLC.


Kim J.,ZEN21 | Choi J.,Pukyong National University | Choi C.,Pukyong National University | Park S.,Pukyong National University
Science of the Total Environment | Year: 2013

This study examined the separate and combined impacts of future changes in climate and land use/land cover (LULC) on streamflow in the Hoeya River Basin, South Korea, using the representative concentration pathway (RCP) 4.5 and 8.5 scenarios of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC). First, a LULC change model was developed using RCP 4.5 and RCP 8.5 storylines and logistic regression. Three scenarios (climate change only, LULC change only, and climate and LULC change combined) were established, and the streamflow in future periods under these scenarios was simulated by the Soil and Water Assessment Tool (SWAT) model. Each scenario showed distinct seasonal variations in streamflow. Under climate change only, streamflow increased in spring and winter but decreased in summer and autumn, whereas LULC change increased high flow during wet periods but decreased low flow in dry periods. Although the LULC change had less effect than climate change on the changes in streamflow, the effect of LULC change on streamflow was significant. The result for the combined scenario was similar to that of the climate change only scenario, but with larger seasonal changes in streamflow. Although the effects of LULC change were smaller than those caused by climate change, LULC changes may heighten the problems of increased seasonal variability in streamflow caused by climate change. The results obtained in this study provide further insight into the availability of future streamflow and can aid in water resource management planning in the study area. © 2013 Elsevier B.V.


Lee S.,Pukyong National University | Kim J.,ZEN21 | Jung Y.,Pukyong National University | Choi J.,Pukyong National University | Choi C.,Pukyong National University
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2012

Much research have been carried out using optimization algorithms for developing high-performance program, under the parallel computing environment with the evolution of the computer hardware technology such as dual-core processor and so on. Then, the studies by the parallel computing in geodesy and surveying fields are not so many. The present study aims to reduce running time for the geoid heights computation and carrying out least-squares collocation to improve its accuracy using distributed parallel technology. A distributed parallel program was developed in which a multi-core CPU-based PC cluster was adopted using MPI and OpenMP library. Geoid heights were calculated by the spherical harmonic analysis using the earth geopotential model of the National Geospatial-Intelligence Agency(2008). The geoid heights around the Korean Peninsula were calculated and tested in diskless-based PC cluster environment. As results, for the computing geoid heights by a earth geopotential model, the distributed parallel program was confirmed more effective to reduce the computational time compared to the sequential program. © 2012 ISPRS.


Kim J.,ZEN21 | Lee S.,Pukyong National University | Ahn H.,Pukyong National University | Seo D.,Pukyong National University | And 3 more authors.
Measurement: Journal of the International Measurement Confederation | Year: 2013

This paper introduces a smartphone-based technique for coastal monitoring and evaluates the accuracy of data such as images, three-dimensional coordinates, and attitude that can be acquired by such a technique. First, to determine intrinsic orientation (IO) parameters of a smartphone camera, a camera calibration was performed. The results were similar or slightly better than previous studies using a non-metric camera. 3-D coordinates provided by the assisted GPS (A-GPS) embedded in the smartphone showed lower accuracy. Attitudes calculated using an accelerometer and magnetometer showed 0.33-2.04° standard deviation, compared with ω, and κ of extrinsic orientation (EO) parameters. Additionally, accuracy (RMSE 0.681 pixels) of smartphone image triangulation using ground control points (GCPs) was about equal to the RMSE of 0.404 pixels of a metric camera. Finally, ortho-rectified images of a test field were generated using DEM from terrestrial laser scanning and acquired images. Additionally, mapping of a shoreline was performed using the ortho-rectified images, and a profile of a representative cross-shore was composed. The results described the actual intertidal zone well. Given the results of the cross-shore profile and the horizontal and vertical accuracy evaluation of the extracted shoreline, this smartphone-based technique is considered appropriate for applications in coastal monitoring. © 2012 Elsevier Ltd. All rights reserved.


Kim J.,ZEN21 | Lee S.,Pukyong National University | Ahn H.,Pukyong National University | Seo D.,Geocean | And 2 more authors.
ISPRS Journal of Photogrammetry and Remote Sensing | Year: 2013

Smartphones can be operated in a 3G network environment at any time or location, and they also cost less than existing photogrammetric UAV systems, providing high-resolution images and 3D location and attitude data from a variety of built-in sensors. This study aims to assess the feasibility of using a smartphone as the payload for a photogrammetric UAV system. To carry out the assessment, a smartphone-based photogrammetric UAV system was developed and utilized to obtain image, location, and attitude data under both static and dynamic conditions. The accuracy of the location and attitude data obtained and sent by this system was then evaluated. The smartphone images were converted into ortho-images via image triangulation, which was carried out both with and without consideration of the interior orientation (IO) parameters determined by camera calibration. In the static experiment, when the IO parameters were taken into account, the triangulation results were less than 1.28. pixels (RMSE) for all smartphone types, an improvement of at least 47% compared with the case when IO parameters were not taken into account. In the dynamic experiment, on the other hand, the accuracy of smartphone image triangulation was not significantly improved by considering IO parameters. This was because the electronic rolling shutter within the complementary metal-oxide semiconductor (CMOS) sensor built into the smartphone and the actuator for the voice coil motor (VCM)-type auto-focusing affected by the vibration and the speed of the UAV, which is likely to have a negative effect on image-based digital elevation model (DEM) generation. However, considering that these results were obtained using a single smartphone, this suggests that a smartphone is not only feasible as the payload for a photogrammetric UAV system but it may also play a useful role when installed in existing UAV systems. © 2013 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS).


Yun M.H.,Pukyong National University | Kim J.,ZEN21 | Seo D.,Pukyong National University | Lee J.,Pukyong National University | Choi C.,Pukyong National University
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2012

Smartphone can not only be operated under 3G network environment anytime and anyplace but also cost less than the existing photogrammetric UAV since it provides high-resolution image, 3D location and attitude data on a real-time basis from a variety of built-in sensors. This study is aimed to assess the possibility of smartphone as a payload for photogrammetric UAV system. Prior to such assessment, a smartphone-based photogrammetric UAV system application was developed, through which real-time image, location and attitude data was obtained using smartphone under both static and dynamic conditions. Subsequently the accuracy assessment on the location and attitude data obtained and sent by this system was conducted. The smartphone images were converted into ortho-images through image triangulation. The image triangulation was conducted in accordance with presence or absence of consideration of the interior orientation (IO) parameters determined by camera calibration. In case IO parameters were taken into account in the static experiment, the results from triangulation for any smartphone type were within 1.5 pixel (RMSE), which was improved at least by 35% compared to when IO parameters were not taken into account. On the contrary, the improvement effect of considering IO parameters on accuracy in triangulation for smartphone images in dynamic experiment was not significant compared to the static experiment. It was due to the significant impact of vibration and sudden attitude change of UAV on the actuator for automatic focus control within the camera built in smartphone under the dynamic condition. This cause appears to have a negative impact on the image-based DEM generation. Considering these study findings, it is suggested that smartphone is very feasible as a payload for UAV system. It is also expected that smartphone may be loaded onto existing UAV playing direct or indirect roles significantly. © 2012 ISPRS.


Lee S.,Pukyong National University | Choi C.,Pukyong National University | Kim J.,ZEN21
Computers and Geosciences | Year: 2013

This paper describes a hybrid MPI/OpenMP approach to using diskless computing clusters to solve time-consuming problems related to ultra-high-degree and -order spherical harmonic analysis using the EGM2008 geopotential model with least-squares collocation to improve the accuracy of EGM2008-derived geoid heights. The proposed hybrid approach conducted 2190-degree and -order spherical harmonic analysis and least-squares collocation fitting using a cluster system of low-performance nodes and achieved a maximum parallel efficiency of 99%. Calculation of the associated Legendre functions and numerical stability were ensured for both 64 and 128. bits in an EGM2008 spherical harmonic analysis for the Korean Peninsula using parallelization modeling. EGM2008 not only described the gravity field of the Korean Peninsula well, but its results were also very accurate compared to those of other global geopotential models. EGM2008-derived geoid heights were fitted with GPS/leveling data from least-squares collocation, which improved their accuracy. For this procedure, parallelization modeling was used to explore the optimum correlation length representing the highest accuracy. After the geoid heights were fitted, their accuracy was evaluated for several cases to determine the optimum distance of GPS/leveling points for least-squares fitting around the Korean Peninsula, and to determine the optimum correlation length by comparing the various results. A correlation length of 119.4. km showed the best fitting results for the case using 102 GPS/leveling points with 40-km intervals. © 2012 Elsevier Ltd.


PubMed | ZEN21
Type: | Journal: The Science of the total environment | Year: 2013

This study examined the separate and combined impacts of future changes in climate and land use/land cover (LULC) on streamflow in the Hoeya River Basin, South Korea, using the representative concentration pathway (RCP) 4.5 and 8.5 scenarios of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC). First, a LULC change model was developed using RCP 4.5 and RCP 8.5 storylines and logistic regression. Three scenarios (climate change only, LULC change only, and climate and LULC change combined) were established, and the streamflow in future periods under these scenarios was simulated by the Soil and Water Assessment Tool (SWAT) model. Each scenario showed distinct seasonal variations in streamflow. Under climate change only, streamflow increased in spring and winter but decreased in summer and autumn, whereas LULC change increased high flow during wet periods but decreased low flow in dry periods. Although the LULC change had less effect than climate change on the changes in streamflow, the effect of LULC change on streamflow was significant. The result for the combined scenario was similar to that of the climate change only scenario, but with larger seasonal changes in streamflow. Although the effects of LULC change were smaller than those caused by climate change, LULC changes may heighten the problems of increased seasonal variability in streamflow caused by climate change. The results obtained in this study provide further insight into the availability of future streamflow and can aid in water resource management planning in the study area.


Lee S.,Korea Aerospace Research Institute | Jin C.,Korea Aerospace Research Institute | Choi C.,Pukyong National University | Lim H.,Korea Aerospace Research Institute | And 2 more authors.
Journal of Applied Remote Sensing | Year: 2012

This paper presents absolute radiometric calibration coefficients (gains) that explain the relationship between the digital number (DN) and at-sensor radiance for the multispectral camera (MSC) on Korea's first high-resolution satellite (KOMPSAT-2). Absolute radiometric calibration was performed using a reflectance-based method. In addition, the suitability of vicarious results from radiance- and reflectance-based validations was analyzed with reference to IKONOS and QuickBird images. The latter are spectrally similar to KOMPSAT-2 images and have been validated in a large number of studies. For all bands, the R2 values of fitted lines for the gain ranged from 0.82 to 0.94, representing an improvement compared to previous findings for the KOMPSAT-2 MSC. To analyze the suitability of the vicarious results, same-pixel at-sensor radiances across different spectral bands were compared. In all bands, except the red band of QuickBird, the at-sensor radiances of KOMPSAT-2 MSC were highly correlated with those of IKONOS and QuickBird. In addition, same-pixel comparisons of reflectance across different spectral bands showed that the slopes of the least-squares lines for each band were similar to the results of the radiance comparison. The standard deviation among top of atmosphere (TOA) reflectances was within 0.019 for all bands. To calculate the tasseled cap transformation (TCT) coefficients for the KOMPSAT-2 MSC, an empirical method was applied using radiometric normalization. The results were similar to those obtained using the TCT coefficients for IKONOS and QuickBird in the brightness, greenness, and wetness components. The TCT images showed similar patterns. The absolute radiometric calibration coefficients presented here appear to be a good standard for maintaining the optical quality of the KOMPSAT-2 MSC, for which prelaunch, on-board, and vicarious calibration data are lacking. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE).


Park S.,Pukyong National University | Choi C.,Pukyong National University | Kim B.,Pukyong National University | Kim J.,ZEN21
Environmental Earth Sciences | Year: 2013

Every year, the Republic of Korea experiences numerous landslides, resulting in property damage and casualties. This study compared the abilities of frequency ratio (FR), analytic hierarchy process (AHP), logistic regression (LR), and artificial neural network (ANN) models to produce landslide susceptibility index (LSI) maps for use in predicting possible landslide occurrence and limiting damage. The areas under the relative operating characteristic (ROC) curves for the FR, AHP, LR, and ANN LSI maps were 0. 794, 0. 789, 0. 794, and 0. 806, respectively. Thus, the LSI maps developed by all the models had similar accuracy. A cross-tabulation analysis of landslide occurrence against non-occurrence areas showed generally similar overall accuracies of 65. 27, 64. 35, 65. 51, and 68. 47 % for the FR, AHP, LR, and ANN models, respectively. A correlation analysis between the models demonstrated that the LR and ANN models had the highest correlation (0. 829), whereas the FR and AHP models had the lowest correlation (0. 619). © 2012 Springer-Verlag.

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