Validation of the GPS leveling method through the gradient analysis of the geoidal wave. Case study of Ecuador.

We validated the GPS leveling as an alternative to the traditional geometric leveling method. Validation compares the geometric slopes derived from the GNSS positioning technique, heights resulting from geometric leveling campaigns and geoid undulations extracted from the Global Geopotential Model EGM08. This analysis was performed in the Ecuadorian mainland, where we identified areas in which the gradient of the geoidal undulation is less pronounced. The spatialization of the gradient or variation-based methods allowed to analyze the performance of the GPS leveling method, under the hypothesis that less variability in geoid undulation implies less discrepancies in the GPS unevenness. GNSS observations were determined on the leveling plates belonging to the Basic Vertical Control Network. The results of the study are given based on the relative error resulting from the comparison of the traditional differential leveling method with the corresponding values obtained from the GNSS positioning, considering different distances for the spread of unevenness.

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Assessment of the GOCE-Based Global Gravity Models in Canada

GEOMATICA ◽

10.5623/cig2012-025 ◽

2012 ◽

Vol 66 (2) ◽

pp. 125-140 ◽

Cited By ~ 8

Author(s):

E. Sinem Ince ◽

Michael G. Sideris ◽

Jianliang Huang ◽

Marc Véronneau

Keyword(s):

Great Lakes ◽

Rocky Mountains ◽

Spherical Harmonic ◽

Gravity Models ◽

Geopotential Model ◽

Third Generation ◽

Combined Models ◽

Gps Leveling ◽

Global Gravity Models ◽

Geoid Undulations

The aim of this study is to test the first, second and third generation GOCE geoid solutions, obtained from the first 2, 8 and 18-month observations, respectively. These solutions are assessed over Canada and for two sub-regions (the Great Lakes and Rocky Mountains). The Canadian GPS/leveling-derived geoid heights are used as independent control values in the assessment of the GOCE geoid models. The study is conducted in two steps. First, the geoid models are computed from satellite-only models and truncated to different spherical harmonic degrees. These models are compared with the GPS/leveling geoid heights which are reduced to the same spectral band as the satellite models by EGM2008 predicted frequency components higher than the truncation degrees. The results suggest that the GOCE models show a full power of signal up to about spherical harmonic degree 180. Moreover, the second and third generation GOCE models (with the exception of the direct approach models) provide better agreement with the GPS/leveling-derived geoid undulations than the first generation models due to the longer observation period. The second step involves the combination of the two third generation GOCE models with terrestrial data. These models are tested against to the GPS/leveling-derived geoid undulations in full spectrum. EGM2008 global geopotential model and Canadian gravimetric geoid model CGG2005 are also included in the comparisons to measure improvement provided by the GOCE models. The GOCE-combined models yielded GPS/leveling results that are comparable with those obtained from EGM2008 and CGG2005 models. The best comparative results with the combined models give standard deviations of 4.8 cm, 6.0 cm and 12.2 cm for the Great Lakes, Rocky Mountains and Canada, respectively. These results indicate that the third generation GOCE models conform to the Canadian terrestrial gravity data from degrees 90 to 180. The new generation models show evident improvement over the first and second generation models.

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Simulation case study of deformations and landslides using real-time GNSS precise point positioning technique

Geomatics Natural Hazards and Risk ◽

10.1080/19475705.2015.1137243 ◽

2016 ◽

Vol 7 (6) ◽

pp. 1856-1873 ◽

Cited By ~ 6

Author(s):

Raquel M. Capilla ◽

José Luis Berné ◽

Angel Martín ◽

Raul Rodrigo

Keyword(s):

Real Time ◽

Precise Point Positioning ◽

Positioning Technique ◽

Point Positioning

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A High-Resolution Gravimetric Geoid Model for Kuwait Using the Least-Squares Collocation

Frontiers in Earth Science ◽

10.3389/feart.2021.753269 ◽

2022 ◽

Vol 9 ◽

Author(s):

Hamad Al-Ajami ◽

Ahmed Zaki ◽

Mostafa Rabah ◽

Mohamed El-Ashquer

Keyword(s):

High Resolution ◽

Least Squares ◽

Geopotential Model ◽

Gravimetric Geoid ◽

Least Squares Collocation ◽

Geoid Model ◽

Terrestrial Gravity ◽

Digital Elevation ◽

Elevation Model ◽

Gps Leveling

A new gravimetric geoid model, the KW-FLGM2021, is developed for Kuwait in this study. This new geoid model is driven by a combination of the XGM2019e-combined global geopotential model (GGM), terrestrial gravity, and the SRTM 3 global digital elevation model with a spatial resolution of three arc seconds. The KW-FLGM2021 has been computed by using the technique of Least Squares Collocation (LSC) with Remove-Compute-Restore (RCR) procedure. To evaluate the external accuracy of the KW-FLGM2021 gravimetric geoid model, GPS/leveling data were used. As a result of this evaluation, the residual of geoid heights obtained from the KW-FLGM2021 geoid model is 2.2 cm. The KW-FLGM2021 is possible to be recommended as the first accurate geoid model for Kuwait.

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

ISPRS International Journal of Geo-Information ◽

10.3390/ijgi10120819 ◽

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.

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Assessing the quality of GEOID12B model through field surveys

Journal of Applied Geodesy ◽

10.1515/jag-2017-0013 ◽

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.

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