• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2003.10a
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• pp.237-242
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• 2003

During the past, digital orthophoto is generated for rural area or low resolution image, because the accurate extraction of DEM is difficult for urban area. But, nowadays, high resolution DEM by ALS system starts to become available for urban area, so the importance of large scale digital orthophoto generation becomes increasing. In this paper, we propose and describe effective algorithm for detecting occlusion area and not only restoring occlusion area but also processing null pixels by occlusion area for minimizing the heterogeneity of digital orthophoto. With proposed algorithm, we detected occlusion area due to height of structures such as buildings, bridges, etc, and restored occlusion area using reference image. Also, The homogeneity of generated digital orthophoto was improved by using brightness correction.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.988-990
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• 2003

IKONOS image mapping is being considered a possible replacement to the traditional mapping in many countries due to their ease of access to current data and their potential high resolution. Survey Department of His Majesty's Government completed traditional orthophoto mapping of all urban and semi-urban areas of the country. The 1:5000 monochrome orthophoto maps of Kathmandu Valley were completed in 2003. In 2002, as a test, production of a near natural colour Image Map at 1:5000 scale of a part of Kathmandu Valley based on IKONOS data was carried out. A conventional line map plotting of the same area at 1:5000 was also prepared. The objective of the pilot project was to assess the geometric accuracy and the information content of these maps. The details of the study and their results are underlined. The findings of the study helps to explain whether IKONOS image map can replace conventional orthophoto map at 1:5,000 for urban areas of Nepal like Kathmandu.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.5
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• pp.890-896
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• 2006

It's very difficult to acquire the accurate GCP(Ground Control Point) in the urban center and forest aerial photo because of occurring of irregular multi-path error. The purpose of this study is to apply the CPS and the EDM system for 3D orthophoto in the small areas. GCPs surveyed by accuracy triangulation from EDM after from triangulation points to a fiducial point at study area used to GPS. And I have a comment on how to use areal orthophoto for future 3D-GIS after 3D-Modelling using areal orthophoto. As the results, EDM surveying could resolve multi-path error according to GPS surveying and It is possible for using aerial orthophoto on the basis of the 3D-GIS database.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.22 no.4
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• pp.349-357
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• 2004

In order to manage the waterfront efficiently, we are to find the efficiency of producing method for digital orthophoto that presents natural form on lands and digital orthophoto cadastral map that presents the range of physical situation and property on lands in this study. Through this study, We can check that digital orthophoto cadastral maps for the boundary management of the waterfront are utilized widely at various field except the main purpose. Thus, we resolve the leading subjects that include the accuracy evaluation on produced maps and the bond edge of map sheet for the cadastral maps in order to drive activistic utilization and application.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.20 no.2
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• pp.137-143
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• 2002

In this study we generated digital orthophoto from LIDAR data. To generate digital orthophoto, we make TIN from raw laser scanning data(XYZ point data) and compiled DSM from this TIN. In this procedure much noise appeared along the break lines in DSM and this can give bad effect to the quality of digital orthophoto. Therefore, we applied various techniques which can refine the break line. In the result, we concluded that the fusion of LIDAR DEM of lowland and extracted buildings was adequate to generating DSM. So we generated the digital orthophoto from DSM generated from this technique. In the result of quality test, the positional accuracy of this digital orthophoto was better than the positional accuracy of 1:5,000 map.

• Journal of Korean Society for Geospatial Information Science
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• v.1 no.2 s.2
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• pp.83-96
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• 1993

The orthophto map is seen as the form of picture with the uniform reduced scale as the current terrain map. Thus it provides a reasonable feeling of scene and is easy to be interpreted. Furthermore, digital orthophoto is currently used as the basic terrain information data of the Geo-Spatial Information System(GSIS). Therefore, the orhtophoto map has high potential use as a future terrain map. This paper studies the method of producing orthophoto map by using the digital satellite imagery data taken from SPOT satellite of France. The production of orthophoto map requires the process of generating orthophoto imagery with digital elevation model, which process is called digital differential rectification. As the final accuracy of orthophoto map depends on that of digital elevation model, the precise and efficient production method of digital elevation model should be preceded. This study investigated the method of producing digital elevation model directly from SPOT satellite imagery and generated ortho-image by resampling the original SPOT imagery through digital differential rectification. Finally, Simple orthophoto map was made by overlaying the ortho-image and the contour map from digital elevation model.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.23 no.3
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• pp.303-312
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• 2005

Digital map, DEM and orthophoto were produced by using PC based digital photogrammetric system and aerial photo images that were obtained with scale of 1/5,000 and scanning density of 1200dpi and 600dpi, and the accuracies of these outputs were evaluated by various methods. Non-skilled operator produced digital map with PC based digital photogrammetric system and aerial photo images scanned by 1200dpi. The results showed that it was impossible to insert contour lines, but the rest elements could be drawn with the accuracy of 1/1,000. In automatic generation of DEM, scanning density of aerial photo and grid interval of DEM didn't affect the accuracy of DEM. In production of orthophoto, we could know that the larger grid interval of DEM, the lower accuracy of orthophoto, but scanning density of original image had more effect on quality of orthophoto. By the way, accuracy comparison between orthophoto and digital map with same check points showed that orthophoto was more accurate than digital map, and orthophoto could be used in more diverse areas. Hereafter in civilian part, aerial photo image and PC based digital photogrammetric system could make practical application of data correction and update in GIS.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2007.04a
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• pp.273-276
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• 2007

In this study, we generated DSM(Digital Surface Model)s and orthophotos with both LIDAR data and scanned aerial photos and compared them with those generated from only the scanned photos. We checked the relief displacements of buildings appearing in the generated orthophotos, where the displacement should not be exist in a true-orthophoto. The RMSE of the relief displacement in the orthophoto generated using a LIDAR DSM is 3 m while the RMSE in the orthophotos from a DSM based on the image matching is 6.1 m. It was revealed that the orthophoto from a LIDAR DSM are closer to a true-orthophoto. But the results in the accuracy test and similarity evaluation of the generated orthophotos were contrary to former results because the roof texture of buildings were expanded to occlusion areas around the buildings. With the central area of the photo, we can generate sufficiently accurate true-orthophotos using a LIDAR DSM.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.17 no.3
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• pp.233-243
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• 1999

In this study, sample sites are chosen where digitalized cadastral maps are available, and boundaries of forestry, farming lands, and residence are clearly distinguishable. Digital orthophotos, produced from aerial photographs, are overlaid with digitalized cadastral maps to grope for applications of digital orthophoto in cadastre. The conclusions and applicable fields of this study are as follows. The first. digital orthophoto is applicable to solve problems such as discordance and duplication of boundary produced in the process of digitizing cadastral maps. The second, using digital orthophoto, it is possible to extract regions where a trouble of ownership would exist and so the necessity of cadastral resurveying can be brought. The third, by overlaying digital orthophoto and cadastral map, it can be used effectively for the present situation maintenance of buildings. The fourth, because it is possible to examine current land use of each lot, digital orthophoto may contribute to decide the validity of land category on cadastral map.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3D
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• pp.417-422
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• 2008

With standard orthorectification algorithms, one can produce unacceptable structure duplication in the orthophoto due to the double projection. Because of the abrupt height differences, such structure duplication is a frequently occurred phenomenon in the dense urban area which includes multi-history buildings. Therefore, occlusion area detection especially for the urban area is a critical issue in generation of true orthophoto. This paper deals with occlusion area detection with visible height based approach from aerial imagery and LiDAR. In order to accomplish this, a grid format DSM is produced from the point clouds of LiDAR. Next, visible height based algorithm is proposed to detect the occlusion area for each camera exposure station with DSM. Finally, generation of true orthophoto is presented with DSM and previously produced occlusion maps. The proposed algorithms are applied in the Purdue campus, Indiana, USA.