Computations of Geoid Undulation from Comparison of GNSS/Levelling with EGM 2008 for Geodetic Applications

Oluyori, Paul Dare; Ono, Matthew Nnonyelu; Eteje, S. O.

doi:10.29322/ijsrp.8.10.2018.p8230

Cited by 12 publications

(8 citation statements)

References 4 publications

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“…Microsoft Excel programs were developed with the computed models' parameters. The RMSE, as well as the accuracy of the models, were respectively computed with equations (19).…”

Section: Data Processingmentioning

confidence: 99%

Comparison of Three Gravimetric-Geometric Geoid Models for Best Local Geoid Model of Benin City, Nigeria

Oduyebo¹,

Ono²,

Eteje³

2019

IJAERS

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The conversion of geometric as well as ellipsoidal heights from GNSS observations to practical heights for engineering constructions has necessitated the determination of the local geoid model of areas. Benin City is a developing area which requires a local geoid model for conversion of geometric heights to orthometric heights for physical developments in the area. This paper is on the best local geoid model of Benin City, Nigeria by comparing three gravimetric-geometric geoid models of the study area. GNSS and gravimetric observations were carried out on 49 points to respectively obtain their coordinates and absolute gravity values. The theoretical gravity values of the points were computed on the Clarke 1880 ellipsoid, subtracted from the absolute gravity values and corrected for the air (free air) to obtain the free air gravity anomalies of the points. The computed free air gravity anomalies were applied to compute the geoid heights of the points using the integration of the modified Stokes integral. Three geometric geoid surfaces (plane, second degree and third degree surfaces) were fitted to the computed gravimetric geoid heights using the least squares technique to obtain the gravimetric-geometric geoid models of the study area. The RMSE of the three gravimetric-geometric geoid models were computed to determine their (the models) accuracy. The three gravimetric-geometric geoid models were compared using their accuracy to obtain the most suitable geoid model of the study area. The results of the comparison showed that the third degree gravimetric-geometric geoid model is most suitable for application in the study area. It is recommended that ellipsoidal heights obtained from GNSS observation within Benin City, Nigeria should be converted to orthometric heights using the third degree geoid model.

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“…Microsoft Excel programs were developed with the computed models' parameters. The RMSE, as well as the accuracy of the models, were respectively computed with equations (19).…”

Section: Data Processingmentioning

confidence: 99%

Comparison of Three Gravimetric-Geometric Geoid Models for Best Local Geoid Model of Benin City, Nigeria

Oduyebo¹,

Ono²,

Eteje³

2019

IJAERS

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“…These models have been developed over time starting from satellite gravimetric measurements and modelling the shape of the geoid using of a certain number (up to 2190) of spherical harmonics. Another way to compute the geoid undulation is to compare over a common point the difference between its ellipsoidal height defined using a GNSS receiver and its pseudo-orthometric height measured through spirit levelling [2][3][4]. This cannot be done at the global scale because of limitations in the application of spirit levelling, but it can be useful at the regional scale.…”

Section: Introductionmentioning

confidence: 99%

Definition of the Local Geoid Undulation Using Non-contemporary GNSS-Levelling Data on Subsidence Area: Application on the Adriatic Coastline

Tavasci

Vecchi

Gandolfi

2022

Communications in Computer and Information Science

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The knowledge of the so-called geoid undulation, which represents the height of the geoid above a reference ellipsoid, is a fundamental step to link ellipsoidal heights measured using satellite systems and orthometric heights. Several geoid models are available at the time both at the national or global scale, which can be used for the purpose. Another way to define the geoid undulation is to perform joint measures with GNSS and spirit levelling over common benchmarks. This requires onerous measurements that is seldom possible to perform due to their cost. In this work, we evaluated the possibility to define a local model of the geoid undulation using already available spirit levelling orthometric heights and GNSS ellipsoidal heights measured about 13 years later. The test area is the Emilia-Romagna Adriatic coastline, an area of great interest both from the environmental and economic point of view, which is also undergoing consistent subsidence phenomena.Test results show that the available measurements allow defining a geoid undulation that is coherent with the shape defined by the gravimetric models and also allows to transform ellipsoidal heights into orthometric ones more consistent with the height reference available on the surveyed area. A 7 cm overall bias with respect to the ITALGEO05 was found, whereas ITG2009 and EGM2008 have higher differences. The use of subsidence models to align over time the coordinates used to define the geoid undulation has proven to be a fundamental step. The analysis on the a-priori uncertainty in the geoid height definition shown that the combined use of much more precise GNSS coordinates and contemporary spirit levelling campaign is necessary to significantly improve the resulting geoid height.

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“…Thus, spirit leveling has been continuously used to determine (orthometric) height so as to coincide with the local vertical datum in each case and to ensure precision, despite the widespread use of GNSS in the field of surveying. However, GNSS-derived height determination, which is a modern technique that calculates elevation as the difference between the ellipsoidal and geoidal heights, is now being used, following the development of a precise local geoid [1][2][3][4][5][6]. To make it clear, the technique to calculate the elevation based on GNSS and the geoid model is called GNSS-derived height determination, and the calculation result is called elevations in this study.…”

Section: Introductionmentioning

confidence: 99%

Analyzing Precision and Efficiency of Global Navigation Satellite System-Derived Height Determination for Coastal and Island Areas

2021

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The global navigation satellite system (GNSS)-derived height determination technique is applied in the field of surveying owing to the broad use of GNSS and the development of precise local geoid models. In Korea, this technique was officially adopted in 2020 for public surveying, such as urban facility mapping; it is also treated as an efficient way to unify the vertical datum of the inland and island areas of Korea. Here, GNSS surveying was conducted on 19 stations located in Korea’s coastal regions and islands, and GNSS-derived elevations were determined. When each GNSS-derived elevation was compared with elevations from spirit leveling, all stations showed differences of less than 3 cm when GNSS surveying was conducted for 4 h/day over two days; they were smaller than 5 cm with 2 h of surveying. These differences meet the standards of GNSS-derived elevations in Korea. In addition, GNSS-derived elevations were compared with those obtained via sea-crossing leveling in two regions, showing differences smaller than 1 cm. Sea-crossing leveling takes longer than GNSS-derived height determination, and its accuracy can be significantly affected by various environments, such as sea fog. Thus, GNSS-derived height determination represents a practical and useful technique.

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Computations of Geoid Undulation from Comparison of GNSS/Levelling with EGM 2008 for Geodetic Applications

Cited by 12 publications

References 4 publications

Comparison of Three Gravimetric-Geometric Geoid Models for Best Local Geoid Model of Benin City, Nigeria

Comparison of Three Gravimetric-Geometric Geoid Models for Best Local Geoid Model of Benin City, Nigeria

Definition of the Local Geoid Undulation Using Non-contemporary GNSS-Levelling Data on Subsidence Area: Application on the Adriatic Coastline

Analyzing Precision and Efficiency of Global Navigation Satellite System-Derived Height Determination for Coastal and Island Areas

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