• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.4
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• pp.171-188
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• 2013

Landuse changes and cadastral information error categories in the four major river areas were analyzed for the use of policy data as cadastral re-arrangement of national and public lands would be required, using high-resolution air-photographs and cadastral maps before and after the river development. The study sites were the river areas of 40km around four dams of the Nakdong river where their landuses were changed most. As the results, national and public lands reached 79.9% of land parcels and 93.3% of land areas of the study sites similar with those of the four river areas, 84.3% of land parcels and 85.5% of land areas. The landuse classification of the study sites before the four river development was consisted most of 'river'(71.6%) and 'rice field'(12.3%), but after the development the 'river' was reduced to 42.7% and 'park area'(19.6%) including sport fields and 'mixed lots'(20.8%) were increased. Also, 86.7% of land parcels before the development could be reduced after the development if administrative districts and land ownerships were not considered. Cadastral information error categories can be found as cadastral polygon missing, polygon overlap, location and boundary non-coincidence, small polygon generation, and non-coincidence between cadastral boundary and river boundary. Landuse change monitoring method using air-photographs will be useful to analyze landuse state through fast information aquisition and to manage properties of national and public lands such as river areas.

• Spatial Information Research
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• v.22 no.5
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• pp.65-75
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• 2014

Bus headway plays an important role not only in determining the passenger waiting time and bus service quality, but also in influencing the bus operation cost and passenger demand. Previous research on headway control has considered only an hourly difference in the distribution of ridership between peak and non-peak hours. However, this approach is too simple to help manage ridership demand fluctuations in a short time scale; thus passengers' waiting cost will be generated when ridership demand exceeds the supply of bus services. Moreover, bus ridership demand varies by station location and traffic situation. To address this concern, we propose a headway control algorithm for minimizing the waiting time cost by using Smart Card data. We also provide proof of the convergence of the algorithm to the desired headway allocation using a set of preconditions of political waiting time guarantees and available fleet constraints. For model verification, the data from the No. 143 bus line in Seoul were used. The results show that the total savings in cost totaled approximately 600,000 won per day when we apply the time-value cost of waiting time. Thus, we can expect that cost savings will be more pronounced when the algorithm is applied to larger systems.

• Journal of the Korean GEO-environmental Society
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• v.22 no.2
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• pp.35-39
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• 2021

Photogrammetry using drone can produce high-resolution ortho image and acquire high-accuracy 3D information, which is useful. Therefore, this study attempted to determine the possibility of using drone-photogrammetry in park construction by producing a topographic map using drone-photogrammetry and analyzing the problems and accuracy generated during production. For this purpose, we created ortho image and DSM (digital surface model) using drone images and created topographic status map by vectorizing them. Accuracy was compared based on topographic status map by GPS (global positioning system) and TS (total station). The resulting of analyzing mean of the residuals at check points showed that 0.044 m in plane and 0.066 m in elevation, satisfying the tolerance range of 1/1,000 numerical maps, and result of compared lake size showed a difference of about 4.4%. On the other hand, it was difficult to obtain accurate height values for terrain in which existed vegetation when producing the topographic map, and in the case of underground buried objects, it is not possible to confirm it in the image, so direct spatial information acquisition was necessary. Therefore, it is judged that the topographic status map using drone photogrammetry can be efficiently constructed if direct spatial data acquisition is achieved for some terrain.

• Korean Journal of Remote Sensing
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• v.38 no.6_1
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• pp.1301-1314
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• 2022

Normalized Difference Vegetation Index (NDVI) is utilized as an indicator to represent the vegetation condition on the land surface in various applications such as land cover, crop yield, agricultural drought, soil moisture, and forest disaster. However, satellite optical sensors for visible and infrared rays cannot see through the clouds, so the NDVI of the cloud pixel is not a valid value for the land surface. This study proposed a real-time correction of the underestimation noise for GEO-KOMPSAT-2A (GK2A) daily NDVI and made sure its feasibility through the quantitative comparisons with Moderate Resolution Imaging Spectroradiometer (MODIS) NDVI and the qualitative interpretation of time-series changes. The underestimation noise was effectively corrected by the procedures such as the time-series correction considering vegetation phenology, the outlier removal using long-term climatology, and the gap filling using rigorous statistical methods. The correlation with MODIS NDVI was higher, and the difference was lower, showing a 32.7% improvement compared to the original NDVI product. The proposed method has an extensibility for use in other satellite products with some modification.

• Korean Journal of Remote Sensing
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• v.38 no.5_1
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• pp.647-660
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• 2022

To prepare an atmospheric correction model suitable for CAS500-4 (Compact Advanced Satellite 500-4), this letter examined an atmospheric correction experiment using Sentinel-2 images having similar spectral characteristics to CAS500-4. Studies to compare the atmospheric correction results depending on different Aerosol Optical Depth (AOD) data are rarely found. We conducted a comparison of Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes (FLAASH), Sen2Cor, and Second Simulation of the Satellite Signal in the Solar Spectrum - Vector (6SV) version 1.1 and 2.1, using Geo-Kompsat 2A (GK2A) Advanced Meteorological Imager (AMI) and Aerosol Robotic Network (AERONET) AOD data. In this experiment, 6SV2.1 seemed more stable than others when considering the correlation matrices and the output images for each band and Normalized Difference Vegetation Index (NDVI).

• Journal of the Korean GEO-environmental Society
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• v.14 no.9
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• pp.49-56
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• 2013

Looking at the changes in the earthquake of 33 years of South Korea, earthquake in the magnitude of 3.0 or stronger have been conducted about nine times a year on average, and the epicenter of the earthquake is moving towards the inland from the coast. As the possibility of earthquakes increase, it is time to require utilization of underground space integrated information for earthquake disaster prevention. But, now the data related to the characterization of the ground and geology in the areas weak against earthquakes is insufficient, so we need to collect new geology and the ground survey data on nationwide scale and have to establish earthquake disaster prevention plans through the joint use of the existing underground space information. In this study, we determined the scope of construction of underground space DB information that is needed for earthquake disaster prevention, presented the construction plan of DB static and dynamic information of underground space. It also suggested the utilization of underground space scheme information for built earthquake disaster prevention. The underground space information for earthquake disaster prevention that was built through determining the scope and constructing, planning the utilization of underground space information is supposed to used as DB of the integrated management system of underground space and steep slopes information for steep slopes and earthquake prevention by Emergency Management Agency.

• Journal of Korean Society for Geospatial Information Science
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• v.13 no.3 s.33
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• pp.69-77
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• 2005

Most of the evaluations of environmental effect of construction of road do not run parallel with the evaluation of the propriety of the business, but it just reviews how to reduce contamination before the beginning of the construction work. This reveals the limitation of the induction of environment friendly development from the fundamental. In this study, a function of GIS spatial analysis for 9 elements of pre-evaluation of environmental effect has been introduced, and a GIS decision making system for environmental effect of a road has been established for an integrated evaluation by using individual evaluation result. By using GIS decision making system for pre-evaluation of environmental effect that has been developed in this study and the GIS data that has been collected, it would be possible to decrease time and money for evaluation as well as fulfill the requirement of objectivity. Therefore, it would be possible to apply for pre-evaluation of environmental effect when deciding on the route of the road at the beginning stage of the construction work. Also, through the system developed in this study, the construction body could easily induce a mutual agreement with the residents by the visual evaluation material, which might result in an evaluation of environmental effect while decreasing time and money at the beginning stage of the construction.

• Spatial Information Research
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• v.20 no.4
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• pp.83-92
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• 2012

Location-based services (LBS) are increasingly popular due to the improvement of geo-positioning capabilities and wireless communication technology. However, in order to enjoy LBS services, a user requesting a query must send his/her exact location to the LBS provider. Therefore, it is a key challenge to preserve user's privacy while providing LBS. To solve this problem, the existing method employs a 2PASS cloaking framework that not only hides the actual user location but also reduces bandwidth consumption. However, 2PASS does not fully guarantee the actual user privacy because it does not take the real user distribution into account. Hence, in this paper, we propose a nearest neighbor query processing algorithm that supports K-anonymity property based on the weighted adjacency graph(WAG). Our algorithm not only preserves the location of a user by guaranteeing k-anonymity in a query region, but also improves a bandwidth usage by reducing unnecessary search for a query result. We demonstrate from experimental results that our algorithm outperforms the existing one in terms of query processing time and bandwidth usage.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.19 no.4
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• pp.327-335
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• 2001

This paper present to how to make VGIS(Virtual Geographic Information System) using GIS and digital map. Because the development of the GIS has been 2-dimension in the last few years, viewpoint of the high-resolution image estimate was difficult. The geo-spatial information system has lots of errors in the policy decision and the principal decision making because it was displayed as 2 dimension map that the digital map and topographical map, geological map. agronomical map, cadastral map and underground facility map are expressed as a symbol practically in spite that it is spatial topography data. It is utilized as effective administration analyzing, all kinds of discussion, transportation and environmental effect evaluation, various kinds of building discussion and policy decision thorough researching the present condition of region as 3 dimension map using digital map and GIS when drafting and deciding all kinds of urban plaining so it is considered that errors of policy decision will be minimized.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.43 no.2
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• pp.113-119
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• 1998

Spatial patterns of soil temperature on sloping lands are related to the amount of solar irradiance at the surface. Since soil temperature is a critical determinant of many biological processes occurring in the soil, an accurate prediction of soil temperature distribution could be beneficial to agricultural and environmental management. However, at least two problems are identified in soil temperature prediction over natural sloped surfaces. One is the complexity of converting solar irradiances to corresponding soil temperatures, and the other, if the first problem could be solved, is the difficulty in handling large volumes of geo-spatial data. Recent developments in geographic information systems (GIS) provide the opportunity and tools to spatially organize and effectively manage data for modeling. In this paper, a simple model for conversion of solar irradiance to soil temperature is developed within a GIS environment. The irradiance-temperature conversion model is based on a geophysical variable consisting of daily short- and long-wave radiation components calculated for any slope. The short-wave component is scaled to accommodate a simplified surface energy balance expression. Linear regression equations are derived for 10 and 50 cm soil temperatures by using this variable as a single determinant and based on a long term observation data set from a horizontal location. Extendability of these equations to sloped surfaces is tested by comparing the calculated data with the monthly mean soil temperature data observed in Iowa and at 12 locations near the Tennessee - Kentucky border with various slope and aspect factors. Calculated soil temperature variations agreed well with the observed data. Finally, this method is applied to a simulation study of daily mean soil temperatures over sloped corn fields on a 30 m by 30 m resolution. The outputs reveal potential effects of topography including shading by neighboring terrain as well as the slope and aspect of the land itself on the soil temperature.