Geoid Undulation, Interpretation

2020 ◽  
pp. 1-5
Author(s):  
Petr Vaníček
Keyword(s):  
Geoid Undulation

scholarly journals Combining Global Geopotential Models, Digital Elevation Models, and GNSS/Leveling for Precise Local Geoid Determination in Some Mexico Urban Areas: Case Study

2021 ◽  
Vol 10 (12) ◽  
pp. 819
Author(s):  
Norberto Alcantar-Elizondo ◽  
Ramon Victorino Garcia-Lopez ◽  
Xochitl Guadalupe Torres-Carillo ◽  
Guadalupe Esteban Vazquez-Becerra
Keyword(s):  
Regression Model ◽  
Numerical Integration ◽  
Urban Areas ◽  
Polynomial Regression ◽  
Geodetic Network ◽  
Geoid Undulation ◽  
Geopotential Model ◽  
Commission Error ◽  
Standard Deviations ◽  
Polynomial Regression Model

This work shows improvements of geoid undulation values obtained from a high-resolution Global Geopotential Model (GGM), applied to local urban areas. The methodology employed made use of a Residual Terrain Model (RTM) to account for the topographic masses effect on the geoid. This effect was computed applying the spherical tesseroids approach for mass discretization. The required numerical integration was performed by 2-D integration with 1DFFT technique that combines DFT along parallels with direct numerical integration along meridians. In order to eliminate the GGM commission error, independent geoid undulations values obtained from a set of GNSS/leveling stations are employed. A corrector surface from the associated geoid undulation differences at the stations was generated through a polynomial regression model. The corrector surface, in addition to the GGM commission error, also absorbs the GNSS/leveling errors as well as datum inconsistencies and systematic errors of the data. The procedure was applied to five Mexican urban areas that have a geodetic network of GNSS/leveling points, which range from 166 to 811. Two GGM were evaluated: EGM2008 and XGM2019e_2159. EGM2008 was the model that showed relatively better agreement with the GNSS/leveling stations having differences with RMSE values in the range of 8–60 cm and standard deviations of 5–8 cm in four of the networks and 17 cm in one of them. The computed topographic masses contribution to the geoid were relatively small, having standard deviations on the range 1–24 mm. With respect to corrector surface estimations, they turned out to be fairly smooth yielding similar residuals values for two geoid models. This was also the case for the most recent Mexican gravity geoid GGM10. For the three geoid models, the second order polynomial regression model performed slightly better than the first order with differences up to 1 cm. These two models produced geoid correction residuals with a standard deviation in one test area of 14 cm while for the others it was of about 4–7 cm. However, the kriging method that was applied for comparison purposes produced slightly smaller values: 8 cm for one area and 4–6 cm for the others.

scholarly journals Vegetation Height Estimation using Satellite Remote Sensing in Peat Land of Central Kalimantan

2021 ◽  
Vol 6 (1) ◽  
pp. 024-034
Author(s):  
Atriyon Julzarika ◽  
Harintaka Harintaka ◽  
Tatik Kartika
Keyword(s):  
Remote Sensing ◽  
Spatial Information ◽  
Geoid Undulation ◽  
Height Estimation ◽  
Central Kalimantan ◽  
Vegetation Height ◽  
Accuracy Test ◽  
Sensing Technology ◽  
The Difference ◽  
Difference Test

Vegetation height is an important parameter in monitoring peatlands. Vegetation height can be estimated using remote sensing. Vegetation height can be estimated by utilizing DSM and DTM. The data that can be used are LiDAR, X-SAR, and SRTM C. In this study, LiDAR data is used for DSM2018 and DTM2018 extraction. The purpose of this research is to detect the vegetation height in Central Kalimantan peatlands using remote sensing technology. The research location is in Bakengbongkei, Kalampangan, Central Kalimantan. The integration of X-SAR and SRTM C is used for DSM2000 and DTM2000 extraction. DSM2000, DTM2000, DSM2018, and DTM2018 performed height error correction with tolerance of 1.96? (95%). Then do the geoid undulation correction to EGM2008. The results obtained are DSM and DTM with a similar height reference field. If it meets these conditions it can be calculated the vegetation height estimation. Vegetation height can be obtained using the Differential DEM method. The Changing in vegetation height from 2000 to 2018 can be estimated from the difference in vegetation height from 2000 to vegetation height in 2018. Results of spatial information on vegetation height and its changes need to be tested for the accuracy. This accuracy-test includes a cross section test, height difference test, and comparison with measurements of vegetation height in the field. The results of this research can be used to monitor the changing the vegetation height in peatlands.

Assessing the quality of GEOID12B model through field surveys

2018 ◽  
Vol 12 (1) ◽  
pp. 1-13
Author(s):  
Ahmed Elaksher ◽  
Franck Kamtchang ◽  
Christian Wegmann ◽  
Adalberto Guerrero
Keyword(s):  
Geoid Undulation ◽  
Kriging Model ◽  
Random Errors ◽  
Dual Frequency ◽  
Field Surveys ◽  
Satellite Systems ◽  
Gnss Receivers ◽  
Orthometric Heights ◽  
Geoid Undulations

AbstractElevation differences have been determined through conventional ground surveying techniques for over a century. Since the mid-80s GPS, GLONASS and other satellite systems have modernized the means by which elevation differences are observed. In this article, we assessed the quality of GEIOD12B through long-occupation GNSS static surveys. A set of NGS benchmarks was occupied for at least one hour using dual-frequency GNSS receivers. Collected measurements were processed using a single CORS station at most 24 kilometers from the benchmarks. Geoid undulation values were driven by subtracting measured ellipsoidal heights from the orthometric heights posted on the NGS website. To assess the quality of GEOID12B, we compared our computed vertical shifts at the benchmarks with those estimated from GEOID12B published by NGS. In addition, Kriging model was used to interpolate local maps for the geoid undulations from the benchmark heights. The maps were compared with corresponding parts of GEOID12B. No biases were detected in the results and only shifts due to random errors were found. Discrepancies in the range of ten centimetres were noticed between our geoid undulation and the values available from NGS.

Accuracy of geoid undulation computations

1973 ◽  
Vol 78 (32) ◽  
pp. 7589-7595 ◽  
Author(s):  
Richard H. Rapp
Keyword(s):  
Geoid Undulation

scholarly journals Computing height anomalies using spherical harmonic coefficients at certain degrees and orders in long-wavelength components

2016 ◽  
Vol 19 (2) ◽  
pp. 11-18
Author(s):  
Bao-Binh Luong
Keyword(s):  
Spherical Harmonic ◽  
Geoid Undulation ◽  
Height Anomaly ◽  
Reliability Of Results ◽  
Long Wavelength ◽  
Basic Quantity ◽  
Near Future

Height anomaly / geoid undulation) is a basic quantity in geodesy. It can be directly measured from GPS and leveling or computed from gravitational models. This paper introduces program GeoH to compute height anomalies using spherical harmonic coefficients at certain degrees and orders in longwavelength components. By reasonably comparing with official values of EGM96, the reliability of results from GeoH is proved for the long-wavelength components, and then can be applied in the “remove-restore” technique for determining Vietnamese quasi-geoid in near future.

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