GPS/Leveling 기법에 의한 정밀지오이드 연구 = A Study on the Precise Geoid Using GPS/Leveling Technique

다국어 초록 (Multilingual Abstract)

It is necessary for utilizing the GPS/Leveling method to determine the detailed geoid, and thus many researchers have developed various geopotential models, which are widely used in our community. To obtain the data for this study, 26 GPS observation points including 23 TBL and 3 triangulation points with an approximately 16-㎞ interval were selected from the Andong geographic map with a scale of 1 : 250,000. These data are implemented to the previously developed gravity models : EGM96, OSU91A, and KGEOID. Deviations between geoid calculated from the geopotential models and geoid obtained from GPS observation, based on the assumption that the levels of TBL and triangulation points are correct, are 0.887m∼0.121m in EGM96 model, 0.580m ∼ -0.028m in OSU91A model, and 0.467m ∼ -0.024m in KGEOID model. The average deviations are 0.493m, 0.277m, and 0.195m, respectively and RMS errors are ±0.299m, ±0.152m, and ±0.133m. Although results shows that the KGEOID model has a better accuracy compared to other models, it is though that models used above are still not good for utilizing the GPS/Leveling method.
Geoid undulations in the study area are 25.70m on Chungju region in Chungbuk Province and 29.80m on Pohang region in Kyungbuk Province, and deviation isabout 4.10m. The general trend of geoid undulations, however, shows an increasing pattern to the NW-SE direction. It has been also reported that geoid undulations are related with topographic highs and geoid highs, but the low R-squared value (0.01677) calculated in this area suggests that the relationship is very poor. Therefore, it is necessary for the enhancement and establishing the more precise model in appropriate to our countrys terrain to do more geoid related observations, and it is also considered other factors including topography in the field of the detailed geoid studying. Especially, the effect of different materials in the subsurface should be considered and geoid models used in this study would be helpful.