• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.29 no.3
• /
• pp.319-325
• /
• 2011

It has been used not orthometric height but normal orthometric height for the official height in Korean benchmark because it has been used not observed gravity but normal gravity for the computation of orthometric correction. The purpose of this study is to propose height renewal method of Korean benchmark. For this purpose, we observed gravity by CG5 digital gravimeter in both the first benchmark line between Sokcho and Gangneung area and the second benchmark line between Soksa and Inje area. We calculated relative gravity value and orthometric correction in all benchmarks. So, the maximum orthometric correction shows -0.349mm in the first benchmark line, and the maximum orthometric correction shows -44.060mm in the second benchmark line. In conclusion, we can confirm that the orthometric correction based on observed gravity is necessary for more accurate official height computation in the Korean benchmark.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.22 no.2
• /
• pp.117-125
• /
• 2004

This paper describes the orthometric correction for determining the orthometric height obtained from height difference by precise leveling or GPS leveling. Five formulas are used to calculate the orthometric correction for two level lines as an examples. Based on the comparison results Strang van Hees' formula that use the surface gravity is better than the others to compute the orthometric corrections on spirit leveling and GPS/Leveling in an area where mean hight is high and terrain relief show high variability. Further research is necessary to improve the results of this study using Mader method, etc..

• Journal of Korean Society for Geospatial Information Science
• /
• v.23 no.3
• /
• pp.41-47
• /
• 2015

To determine the accurate height, it should be considered geometric height difference obtained by levelling as well as the physical height difference what so called orthometric correction. The orthometric correction amount is small enough to ignore at flatland but the amount is big at high mountains, so it should be considered to obtain accurate height at high mountains. But the calculation process is difficult and complex, not easy to calculate. So, to make the process easy using a user-friendly visual, a orthometric correction calculation program Ortho-Calc. v1.0 was developed in this study. This program was adopted the algorithm of Nassar and Hwang & Hsiao, and Strang Van Hees and it could be to selectivily calculate the correction amount. The inspection result exhibited high accuracy with the standard deviation of 0.024mm by the comparison of previous study. Therefore, This program Ortho-Calc. v1.0 developed in this study, will contribute orthometric correction calculation quickly and easily. And, if this program is widely popular, it could be expected to make a contribution the Benchmark's official height renewal using orthometric correction.

• Journal of Cadastre & Land InformatiX
• /
• v.48 no.2
• /
• pp.99-108
• /
• 2018

The purpose of this study is to determine the precise height in mountainous areas of South Korea and Jiri mountain area was selected as a test bed for the study. Gravity observation and GNSS surveying were performed for 44 BM(Benchmark) points in the test bed and calculate the height and the height correction. In the calculation, the dynamic correction amount, the orthometric correction amount and the normal correction amount were calculated, and the dynamic height and orthometric height and the normal height were calculated considering each correction amount. The results showed that the difference between normal gravity and observed gravity and also the difference between orthometric correction and the normal correction. In addition, the results of the comparison of the present official BM height and the computed orthometric height in this study show that Korean height system should be shifted from the normal orthometric height system to the orthometric height system. Because the difference between the orthometric correction and the normal correction within the test bed indicated a distribution of at a minimum of -234.41 mm up to 196.925 mm, and the difference between the present official BM height and the calculated orthometric height were distributed from -0.121m to 0.011 m.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.17 no.2
• /
• pp.61-69
• /
• 2005

The coastal erosion and the look of a heap which are mainly occurred in the district along the coast are found for various forms such as the estuary closing, the estuary sand bar the development of the coast sand bar, and the modification of coastline. Recently, due to the coastal development, these transformations have been intensified. The change of coast, which has been made slow progress is required long-term study on a searching examination of the root cause and a suggestion of a counter measure. In this research, ortho aerial photos were produced to analyze volumes of topographical alternations that have been progressed fer the long run, by 10s cycle from 1940s through 1990s, to compute accurate volumes of coastline variation, through a datum point and G.C.P (Ground Control Point). Also in this study, without respect to water level, the coastline variation was analyzed by using comparatively analyzed a Idlest land map, a cadastral map. And to analyze topographical variation volumes, the tidal station's materials was used under consideration f3r tide. Finally, topographical variation volumes are comparatively analyzed through surveying and sounding and a point of fine of aviation photographing was calculated and revised. After this research, by using ortho aerial photos, We can understand efficiency of these in computing volumes of variations of coastline by analyzing quantitatively erosion and look of a heap. Besides, in the future, these will be used for information gathering of the coastline integration control system.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2010.04a
• /
• pp.39-42
• /
• 2010

This Study describes the mountainous area which is located in Gyeongsangbuk-do and Jeollanam-do used the relative gravimeter in the object and is measured and the gravity data which used orthometric correction, is a physical height the altitude in compliance with the level measurement which is an altitude and a geometric height is really a difference in compliance with the method which is various calculated orthometric height. In addition, calculated by various were compared & analyzed by orthometric correction against the objective area to determine the appropriate orthometric correction method of calculation.

• Proceedings of the Korea Contents Association Conference
• /
• 2009.05a
• /
• pp.485-487
• /
• 2009

The Spatial Image contents of Geomorphology 3-D environment is focused by the requirement and importance in the fields such as, national land development plan, telecommunication facility management, railway construction, general construction engineering, Ubiquitous city development, safety and disaster prevention engineering. The currently used DEM system using contour lines, which embodies geographic information based on the 2-D digital maps and facility information has limitation in implementation in reproducing the 3-D spatial city. Moreover, this method often neglects the altitude of the rail way infrastructure which has narrow width and long length. This As the results, We confirmed the solutions of varieties application for railway facilities management using 3-D spatial image contents and database design. Also, I suggested that U-city using topographical modeling about matching methods of high density elevation value using 3-D aerial photo with laser data are best approach for detail stereo modeling and simulation.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.6
• /
• pp.2593-2600
• /
• 2013

The main purpose of this study is to carry out the performance evaluation of Ultra-light Fixed Wing UAV(Unmanned Aerial Vehicle) photogrammetry which is being, currently, applied for various fields such as cultural assets, accident survey, military reconnaissance work, and disaster management at home and abroad. Firstly, RMSE estimation of Aerial Triangulation (AT) are within approximately 0.10 cm in position (X, Y). And through the comparison of parcel's boundary points coordinates by terrestrial surveying and by UAV photogrammetry, the analysis shows that RMSE are shifted approximately 0.174~0.205 m in X-direction, 0.294~0.298 m in Y-direction respectively. Lastly, parcel's area by orthophoto of UAV photogrammetry and by that of cadastre register has been shown the difference by 0.118 m2. The results presented in this study is just one case study of orthophoto accuracy assessment of Ultra-light fixed wing UAV photogrammetry, hereafter various researches such as AT, direct-georeferencing, flight planning, practical applications, etc. should be necessary continuously.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.20 no.1
• /
• pp.56-70
• /
• 2017

In this study, multi-image information for the central Taewha River basin was used to develop and analyze a distribution map of non-point pollution sources. The data were collected using a hyper-sensor (image), aerial photography, and a field spectro-radiometer. An image correction process was performed for each image to develop an ortho-image. In addition, the spectra from the field spectro-radiometer measurements were analyzed for each classification to create land cover and distribution maps of non-point pollutant sources. In the western region of the Taewha River basin, where most of the forest and agricultural land is distributed, the distribution map showed generated loads for BOD($kg/km^2{\times}day$) of 1.0 - 2.3, for TN($kg/km^2{\times}day$) of 0.06 - 9.44, and for TP($kg/km^2{\times}day$) of 0.03 - 0.24, which were low load distributions. In the eastern region where urbanization is in progress, the BOD, TN, and TP were 85.9, 13.69, and 2.76, respectively and these showed relatively high load distributions when the land use was classified by plot.

• Journal of The Geomorphological Association of Korea
• /
• v.17 no.4
• /
• pp.71-83
• /
• 2010

In this study, the volume of shoreline retreat at sea-cliffs in the Taean peninsula(West Coast of Korea) was estimated and their erosion and seasonal landforms characteristics changes were investigated through multi-temporal aerial photographs and field survey. Based on the analysis of aerial photographs through ortho-correction, the results show that the length of shoreline and erosion area increase as erosion at sea-cliffs occurs in Pado-li and Dundu-li. To obtain the seasonal quantitative landforms changes and retreat of sea-cliffs, we marked top, middle, and bottom datum-points, from which the distance to the nearest bedrock was repeatedly measured. In these regions, the retreat of sea-cliffs gradually increases in spring to summer, but gradually decreases in autumn. In particular, the typhoon that has a great influence on the Korean peninsula in July to September in summer would drastically increase the retreat of sea-cliffs in comparison with other seasons. As the outcrop of sea-cliffs repeats freezing and thawing in winter, the retreat of sea-cliffs increases a little due to active mechanical weathering. To know the erosion and seasonal landforms changes of sea-cliffs, we took pictures of them in every month and then analyze their condition. The retreat of sea-cliffs was repeatedly occurred by the circulation of the erosion of sea-cliff base, landslides, the formation of slope sediment debris and their erosion, in that order.