• Journal of the Korean Association of Geographic Information Studies
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• v.6 no.4
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• pp.85-98
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• 2003

There has recently been an increasing interest of the watershed management as a solution to a wide range of problems related water environment, therefore this study attempted to construct the environment information system to monitor the Geumho River watershed, and to evaluate the impacts of the watershed characteristics on stream water quality. A detailed GIS database to analyze the environmental characteristics at the subwatershed units, including 1:25,000 scale topographical maps, detailed soil maps, land use, 10m-resolution DEMs, roads, streams, vegetation index(NDVI) calculated from Landsat TM imagery, rainfall, and soil loss using RUSLE, is compiled for the study area. The set of variables representing watershed urbanization or industrialization, residential and commercial landuse, industrial landuse, and road area have significantly negative(-) relationship with water quality variables(BOD, COD, SS, T-N, T-P). On the other hand, watershed indicators related to natural environmental conditions, forest cover and vegetation index(NDVI) in each subwatershed were significantly positive(+) relationship with water quality. Three other variables, agricultural landuse, amount of fertilizer and pesticides, and potential soil loss, were not significant in explaining the correlations between watershed environment and stream water quality.

• Journal of the Korean Association of Geographic Information Studies
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• v.8 no.3
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• pp.84-95
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• 2005

This paper presents solution heuristics to solving optimal multiple-viewpoint location problems that are based on topographic features. The visibility problem is to maximise the viewshed area for a set of viewpoints on digital elevation models (DEM). For this analysis, five areas are selected, and fundamental topographic features (peak, pass, and pit) are extracted from the DEMs of the study areas. To solve the visibility problem, at first, solution approaches based on the characteristics of the topographic features are explored, and then, a benchmark test is undertaken that solution performances of the solution methods, such as computing times, and visible area sizes, are compared with the performances of traditional spatial heuristics. The feasibility of the solution methods, then, are discussed with the benchmark test results. From the analysis, this paper can conclude that fundamental topographic features based solution methods suggest a new sight of visibility analysis approach which did not discuss in traditional algorithmic approaches. Finally, further research avenues are suggested such as exploring more sophisticated selection process of topographic features related to visibility analysis, exploiting systematic methods to extract topographic features, and robust spatial analytical techniques and optimization techniques that enable to use the topographic features effectively.

• Journal of the Korean Association of Geographic Information Studies
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• v.13 no.1
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• pp.74-88
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• 2010

In this study, the points of LiDAR were modified in order to generate various DEM resolutions by applying LiDAR data in Ulsan. Since the LiDAR data have points with 1m intervals, the number of points for each resolution was modified to the size of 1, 5, 10, 30, 50, 100m by uniformly eliminating the points. A runoff analysis was performed on Taehwa river and its tributary, Dongcheon, with 200 year rainfall exceedance probability. 2-dimensional inundation analysis was performed based on the density of LiDAR data using FLUMEN, which was used to establish domestic flood risk map. Once DEM data obtained from LiDAR survey are used, it is expected that the study results can be used as data in determining optimal grid spacing, which is economical, effective and accurate in establishing flood defence plans including the creation of flood risk map.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.17 no.2
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• pp.97-104
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• 1999

Digital elevation models(DEMs) represent an important data base for orthophoto generation The quality of a DEM depends on the geometrical accuracy of the original point or line data. This study analyzes the effects of grid space and scanning resolution in DEM creation with image matching method. The less standard deviation of DEM error was introduced when we adopted small grid space, but no effects in scanning resolution. Based on the bias error analysis of the DEM, we found that the error of a large scale of aerial photograph was bigger than that of a small scale case, and that such error mainly came from the closed area in large scale photographs. In order to reduce the closed area, the experiment has been conducted using multi scale and different overlap of aerial photo images. The result shows that the size of closed area and the shaded area has been dramatically decreased due to the adoption of multi scale aerial images instead of a couple of stereo images.

• Korean Journal of Remote Sensing
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• v.33 no.1
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• pp.69-77
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• 2017

S The need for an automated geo-positioning approach for near real-time results and to boost cost-effectiveness has become increasingly urgent. Following this trend, a new approach to automatically compensate for the bias of the rational function model (RFM) was proposed. The core idea of this approach is to remove the bias of RFM only using tie points, which are corrected by matching with the digital elevation model (DEM) without any additional ground control points (GCPs). However, there has to be a additional evaluation according to the quality of DEM because DEM is used as a core element in this approach. To address this issue, this paper compared the quality effects of DEM in the conduct of the this approach using the Shuttle Radar Topographic Mission (SRTM) DEM with the spatial resolution of 90m. and the National Geographic Information Institute (NGII) DEM with the spatial resolution of 5m. One KOMPSAT-2 stereo-pair image acquired at Busan, Korea was used as experimental data. The accuracy was compared to 29 check points acquired by GPS surveying. After bias-compensation using the two DEMs, the Root Mean Square (RMS) errors were less than 6 m in all coordinate components. When SRTM DEM was used, the RMSE vector was about 11.2m. On the other hand, when NGII DEM was used, the RMSE vector was about 7.8 m. The experimental results showed that automated geo-positioning approach can be accomplished more effectively by using NGII DEM with higher resolution than SRTM DEM.

• Journal of Korean Society on Water Environment
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• v.32 no.1
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• pp.89-97
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• 2016

Digital Elevation Models (DEMs) have been used to represent the effects of topography on soil erosion. A DEM of 30 m resolution is frequently used in hydrology and soil erosion studies because the National Water Management Information System (WAMIS) provides a 30 m resolution DEM at national scale on its web site. However, the Ministry of Environment recommends the use of a DEM with 10 m resolution for evaluation of soil erosion due to the fact that soil erosion estimation is to some degree affected by the spatial resolution of DEM. In this regard, a DEM with 5 m resolution was resampled for 10 × 10 m, 20 × 20 m, 30 × 30 m, 50 × 50 m, 70 × 70 m, and 100 × 100 m resolutions, respectively. USLE LS factors and soil erosion values were evaluated using these datasets. Use of a DEM with at least 30 m resolution provided reasonable LS factors and soil erosion values at a watershed.

• Journal of Korean Society for Geospatial Information Science
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• v.20 no.2
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• pp.73-79
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• 2012

This study attempts to analyze changes in land use patterns in a compound urban and agricultural city Kimje-si, using LANDSAT TM imagery and to forecast future changes accordingly. As a new approach to supervised classification, HSB(Hue, Saturation, Brightness)-transformed images were used to select training zones, and in doing so classification accuracy increased by more than 5 percent. Land use changes were forecasted by using a cellular automaton algorithm developed by applying Markov Chain techniques, and by taking into account classification results and GIS data, such as population of the pertinent region by area, DEMs, road networks, water systems. Upon comparing the results of the forecast of the land use changes, it appears that geographical features had the greatest influence on the changes. Moreover, a forecast of post-2030 land use change patterns demonstrates that 21.67 percent of mountain lands in Kimje-si is likely to be farmland, and 13.11 percent is likely to become city areas. The major changes are likely to occur in small mountain lands located in the heart of the city. Based on the study result, it seems certain that forecasting future land use changes can help plan land use in a compound urban and agricultural city to procure food resources.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.19 no.4
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• pp.373-383
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• 2001

This study conducted pilot mapping project to know the possibility of mapping with medium resolution satellite imageries. For this purpose, mapping experiments were conducted with each stereo model imageries of SPOT, KOMPSAT, and IRS- lC. And positional accuracy, analysis of detectable and describable features, and comparison with existing digital map were checked, possible mapping scale and cost analysis were conducted with these results. Regarding SPOT imagery, digital photogrammetric workstation was used for stereoplotting. Regarding KOMPSAT and IRS-lC imageries, because there were data format support problems. head-up digitizing was performed with ortho imageries rectified with DEMs generated by image matching. The results of experiments show that such features as wide road, river, coast line, etc are possible to detect and depict but many other features are not for SPOT, KOMPSAT, and IRS-lC imageries. On the aspect of mapping, therefore, SPOT is available for 1/50,000 topographic map revision, KOMPSAT and IRS-lC for 1/25.000 topographic map revision.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.24 no.2
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• pp.153-158
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• 2006

A new High Resolution Geometry or HRG imaging instrument is developed by CNES to be carried on-board SPOT 5. The HRG instrument offers a higher ground resolution than that of the HRV/HRVIR on SPOT 1 - 4 satellites. The field width of HRG is 60 km, same as SPOT constellation. With two HRG instruments, a maximum swath of 120 km at 5 m resolution can be achieved. The generation of Digital Elevation Models (DEMs) from satellite stereo images scores over conventional methods of DEM generation using topographic maps and aerial photographs. This global availability of satellite images allows for quicker data processing for an equivalent area. In this study, a HRG stereo images of SPOT 5 over JECHEON has been used with Leica Photogrammetry Suite OrthoBASE Pro tool for the creation of a digital elevation model (DEM). The extracted DEM was compared to the reference DEM obtained from the contours of digital topographic map.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.24 no.4
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• pp.367-376
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• 2006

This study determines the optimum polynomial of exterior orientation parameters(EOPs) as a function of line number of linear array scanner. To estimate priori EOPs, meta data of IKONOS scene and ground control points are used. We select a first order polynomial and a constant for position elements modeling and rotation elements modeling. Positioning accuracy of the determined EOPs is compared with that of RPCs bias-corrected by the least squares adjustment. There is almost no difference between accuracies of the two methods. To obtain digital elevation model(DEM), matching line is established by the EOPs. The DEM is compared with DEM generated by ERDAS IMAGINE software, which utilizes the bias-corrected RPCs. Height differences of DEMs by the two methods are ranged within a allowable standard deviation. The produced DEM, therefore, shows accuracy similar to the verified method.