Geometric Geoid Determination in South Korea using GPS/Levelling Data
0
Citation
0
Reference
20
Related Paper
Abstract:
This paper describes the determination of geoid using height data measured by GPS and Spirit Levelling. The GPS data of the 88 stations were used to determine the geoid undulation (N) which can be easily obtained by subtracting the orthometric height(H) from the ellipsoidal height(h). From the geoid undulation (N) calculated at each station mentioned above, geoid plots with a contour interval of 0.25 m were drawn using two interpolation methods. The following interpolation methods were applied and compared with each other: Minimum Curvature Method and Least Squares Fitted Plane. Comparison between geometric geoid and gravimetric geoid undulation by FFT technique was carried out.Keywords:
Levelling
Interpolation
Cite
Interpolation
Dynamic height
Cite
Citations (11)
Geoid has an important role in converting geodetic heights to physical heights, both in orthometric height system and normal height systems. At present, Semarang City already has gravimetric geoid with centimeter-level precision. This gravimetric was validated by geometric geoid measured by static method. GNSS (Global Navigation Satellite System) measurement using static method needs long observation time and costly because it requires network that connect baselines and points. This study aims to implement CORS (Continous Operating Reference Station) GNSS in measuring geodetic height and to apply gravimetric geoid in orthometric height calculations. In this research, the gravimetric geoid recalculation process was carried out using gravity disturbance data of 2016. The geoid fitting process was carried out iteratively based on gravity data and modification of the integral of Hotine. Geodetic height measurements were carried out at 40 points distributed olong 50 km leveling network. Geodetic height measurements were refered to CORS GNSS of BIG (Geospatial Information Agency) and UNDIP (Diponegoro University) to produce standard deviation ranged from ±0.003 m to ±0.055. Geometric geoid checking with previous gravimetric geoid before fitting produced standard deviation of ±0.037 m and datum offset of -0.690 m. Geometric geoid checking for recent gravimetric geoid after fitting produces standard deviation of ±0.043 m and datum offset of -0.010 m. This study concluded that the refering geodetic coordinates to CORS stations by 1 hour observation of rapid static method and processing baselines in commercial software are sufficient for the determination of orthometric height in centimeter-level precision. This study also concluded that gravimetric geoid fitting based on gravity data shifting can minimize datum offset and shrinkage in geoid map.
Dynamic height
Cite
Citations (1)
Dynamic height
Cite
Citations (5)
Levelling
Collocation (remote sensing)
Cite
Citations (25)
AbstractAbstractTransformation of ellipsoidal heights derived from the Global Positioning System (GPS) to orthometric heights using geoid models is investigated in the north and west parts of Turkey. Although the transformation depends on a simple relation between ellipsoidal h, orthometric H and geoid N heights, the accuracy of the resulting orthometric heights after transformation is crucial in geodetic and surveying applications. Various factors which affect this accuracy, such as measurement errors, datum inconsistencies and theoretical assumptions, are investigated in this study, while testing different methods in three test networks (Sakarya in the Northwest, Çankırı in the North and Izmir in the West). The study consists of three steps. In the first step the regional Turkey geoids TG99A, TG03 and the European gravimetric geoid EGG97 are tested comparing geoid heights derived from models and GPS/levelling at co–located benchmarks. In the second step, regional geoid models are combined with GPS/levelling using Least Squares Adjustment of height differences and corrector surface models. In this step, additionally, Variance Component Estimation (VCE) using Minimum Norm Quadratic Unbiased Estimation (MINQUE) approach is performed, in order to combine the height sets. In the last step, GPS/levelling surface type local geoids are determined and their performances are tested in transformation of GPS–heights. Finally, the resulting accuracies are compared and practical aspects of those approaches in deriving orthometric heights from GPS measurements in geodetic and surveying applications are discussed.Keywords: ELLIPSOIDAL HEIGHTSGEOID EGG97GEOID MODELSMINQUE, VARIANCE COMPONENT ESTIMATION
Levelling
Dynamic height
Cite
Citations (28)
The main objective of this study is to improve the geoid by GPS/leveling data in Egypt. Comparisons of the gravimetric geoid with GPS/leveling data have been performed. On the basis of a gravimetric geoid fitted to GPS/leveling by the least square method, a smoothed geoid was obtained. A high-resolution geoid in Egypt was computed with a 2.5′×2.5′ grid by combining the data set of 2600 original point gravity values, 20″×30″ resolution Digital Terrain Model (DTM) grid and the spherical harmonic model EGM96. The method of computation involved the strict evaluation of the Stokes integral with 1D-FFT. The standard deviation of the difference between the gravimetric and the GPS/leveling geoid heights is ±0.47 m. The standard deviation after fitting of the gravimetric geoid to the GPS/leveling points is better than ±13 cm. In the future we will try to improve our geoid results in Egypt by increasing the density of gravimetric coverage.
Gravimetric analysis
Cite
Citations (2)
A new quasi-geoid model for Hungary was determined by combining gravity data, GPS/levelling and vertical deflections. Reduction of the measurements was performed by using Earth Gravitational Model 2008 (EGM2008) and Shuttle Radar Topographic Mission (SRTM) elevation data sets. Calculation method was Least Squares Collocation (LSC) with self-consistent planar logarithmic covariance model. In the computations the weights of GPS/levelling data were large, in this way normal heights obtained from levelling are consistent with GPS heights and with the quasi-geoid model. Astrogeodetic-gravimetric, pure astrogeodetic and pure gravimetric solutions have been calculated besides the combined solution to investigate the discrepancies among the different models. The combined quasi-geoid model fits to the GPS/levelling data with standard deviation of ±4.9 cm, nevertheless at some GPS/levelling sites large differences were indicated.
Levelling
Collocation (remote sensing)
Gravity of Earth
Absolute deviation
Cite
Citations (2)