On Downward Continuing Airborne Gravity Data for Local Geoid Modeling

2021 ◽  
Author(s):  
Xiaopeng Li ◽  
Jianliang Huang ◽  
Martin Willberg ◽  
Roland Pail ◽  
Cornelis Slobbe ◽  
...  
Keyword(s):  
Gravity Data ◽  
Simulated Data ◽  
Real Data ◽  
Airborne Gravity ◽  
Test Bed ◽  
Collective Wisdom ◽  
Resource Limitations ◽  
Work Done ◽  
Local Geoid

<p>The theories of downward continuation (DC) have been extensively studied for many decades, during which many different approaches were developed. In real applications, however, researchers often just use one method, probably due to resource limitations or to finish their work, without a rigorous head-to-head comparison with other alternatives. Considering that different methods perform quite differently under various conditions, comparing results from different methods can help a lot for identifying potential problems when dramatic differences occur, and for confirming the correctness of the solutions when results converge together, which is extremely important for real applications such as building official national vertical datums. This paper gives exactly such a case study by recording the collective wisdom recently developed within  the IAG’s study group SC2.4.1. A total of six normally used DC methods, which are SHA (NGS), LSC (DTU Space), Poisson and ADC (NRCan), RBF (DU Delft), and RLSC (TUM), are applied to both simulated data (in the combination of two sampling strategies with three noise levels) and real data in a Colorado-area test bed. The data are downward continued to both surface points and to the reference ellipsoid surface. The surface points are directly evaluated with the observed gravity data on the topography. The ellipsoid points are then transformed into geoid heights according to NRCan’s Stokes-Helmert’s scheme and eventually evaluated at the GNSS/Leveling benchmarks. In this presentation, we will summarize the work done and results obtained by the aforementioned workgroup.</p>

On Downward Continuing Airborne Gravity Data for Local Geoid Modeling

2020 ◽  
Author(s):  
Xiaopeng Li ◽  
Jianliang Huang ◽  
Cornelis Slobbe ◽  
Roland Klees ◽  
Martin Willberg ◽  
...  
Keyword(s):  
Gravity Data ◽  
The United States ◽  
Downward Continuation ◽  
Continuation Methods ◽  
Airborne Gravity ◽  
Spherical Harmonic Analysis ◽  
Study Group ◽  
Numerical Comparison ◽  
Geoid Model ◽  
Local Geoid

<p>The topic of downward continuation (DWC) has been studied for many decades without very conclusive answers on how different methods compare with each other. On the other hand, there are vast amounts of airborne gravity data collected by the GRAV-D project at NGS NOAA of the United States and by many other groups around the world. These airborne gravity data are collected on flight lines where the height of the aircraft actually varies significantly, and this causes challenges for users of the data. A downward continued gravity grid either on the topography or on the geoid is still needed for many applications such as improving the resolution of a local geoid model. Four downward continuation methods, i.e., Residual Least Squares Collocation (RLSC), the Inverse Poisson Integral, Truncated Spherical Harmonic Analysis, and Radial Basis Functions (RBF), are tested on both simulated data sets and real GRAV-D airborne gravity data in a previous joint study between NGS NOAA and CGS NRCan. The study group is further expanded by adding the TU Delft group on RBF and the TUM group on RLSC to incorporate more updated knowledge in the theoretical background and more in-depth discussion on the numerical results. A formal study group will be established inside IAG for providing the best answers for downward continuing airborne gravity data for local gravity field improvement. In this presentation, we review and compare the four methods theoretically and numerically. Simulated and real airborne and terrestrial data are used for the numerical comparison over block MS05 of the GRAV-D project in Colorado, USA, where the 1cm geoid experiment was performed by 15 international teams. The conclusion drawn from this study will advance the use of GRAV-D data for the new North American-Pacific Geopotential Datum of 2022 (NAPGD2022).</p>

Sedimentary basin analysis using airborne gravity data: a case study from the Bohai Bay Basin, China

2015 ◽  
Vol 105 (8) ◽  
pp. 2241-2252 ◽  
Author(s):  
Wenyong Li ◽  
Yanxu Liu ◽  
Jianxin Zhou ◽  
Xihua Zhou ◽  
Bing Li
Keyword(s):  
Sedimentary Basin ◽  
Gravity Data ◽  
Basin Analysis ◽  
Airborne Gravity ◽  
Bohai Bay ◽  
Bohai Bay Basin

scholarly journals Quasi Geoid and Geoid Modeling with the Use of Terrestrial and Airborne Gravity Data by the GGI Method—A Case Study in the Mountainous Area of Colorado

2021 ◽  
Vol 13 (21) ◽  
pp. 4217
Author(s):  
Marek Trojanowicz ◽  
Magdalena Owczarek-Wesołowska ◽  
Yan Ming Wang ◽  
Olgierd Jamroz
Keyword(s):  
Gravity Data ◽  
Research Work ◽  
Airborne Gravity ◽  
Mountainous Area ◽  
Geoid Model ◽  
Data Inversion ◽  
Gravimetric Quasigeoid ◽  
The Mean ◽  
Grid Points

This article concerns the development of gravimetric quasigeoid and geoid models using the geophysical gravity data inversion technique (the GGI method). This research work was carried out on the basis of the data used in the Colorado geoid experiment, and the mean quasigeoid (ζm) and mean geoid (Nm) heights, determined by the approaches used in the Colorado geoid experiment, were used as a reference. Three versions of the quasigeoid GGI models depending on gravity data were analyzed: terrestrial-only, airborne-only, and combined (using airborne and terrestrial datasets). For the combined version, which was the most accurate, a model in the form of a 1′×1′ grid was calculated in the same area as the models determined in the Colorado geoid experiment. For the same grid, the geoid–quasigeoid separation was determined, which was used to build the geoid model. The agreement (in terms of the standard deviation of the differences) of the determined models, with ζm and Nm values for the GSVS17 profile points, was ±0.9 cm for the quasigeoid and ±1.2 cm for the geoid model. The analogous values, determined on the basis of all 1′×1′ grid points, were ±2.3 cm and ±2.6 cm for the quasigeoid and geoid models, respectively.

scholarly journals Bayesian Adjustment for Insurance Misrepresentation in Heavy-Tailed Loss Regression

Risks ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 83 ◽  
Author(s):  
Michelle Xia
Keyword(s):  
Model Performance ◽  
Simulated Data ◽  
Real Data ◽  
Insurance Premium ◽  
False Statement ◽  
Monte Carlo Techniques ◽  
Large Samples ◽  
Risk Characteristics ◽  
Heavy Tailed

In this paper, we study the problem of misrepresentation under heavy-tailed regression models with the presence of both misrepresented and correctly-measured risk factors. Misrepresentation is a type of fraud when a policy applicant gives a false statement on a risk factor that determines the insurance premium. Under the regression context, we introduce heavy-tailed misrepresentation models based on the lognormal, Weibull and Pareto distributions. The proposed models allow insurance modelers to identify risk characteristics associated with the misrepresentation risk, by imposing a latent logit model on the prevalence of misrepresentation. We prove the theoretical identifiability and implement the models using Bayesian Markov chain Monte Carlo techniques. The model performance is evaluated through both simulated data and real data from the Medical Panel Expenditure Survey. The simulation study confirms the consistency of the Bayesian estimators in large samples, whereas the case study demonstrates the necessity of the proposed models for real applications when the losses exhibit heavy-tailed features.

scholarly journals Geoid Modelling of Kalimantan Island using Airborne Gravity Data and Global Geoid Model (EGM2008)

2021 ◽  
Vol 936 (1) ◽  
pp. 012029
Author(s):  
Zahroh Arsy Udama ◽  
Ira Mutiara Anjasmara ◽  
Arisauna Maulidyan Pahlevi ◽  
Anas Sharafeldin Mohamed Osman
Keyword(s):  
Standard Deviation ◽  
Gravity Anomaly ◽  
Gravity Data ◽  
Airborne Gravity ◽  
Gravimetric Geoid ◽  
Wave Component ◽  
Geoid Model ◽  
Free Air ◽  
Free Air Gravity ◽  
Local Geoid

Abstract The availability of geoids, especially in survey and mapping activities, is useful for transforming the geometric heights obtained from observations of the Global Navigation Satellite System (GNSS) into orthometric heights that have real physical meanings such as those obtained from waterpass measurements. If a geoid is available, the orthometric heights of points on earth can be determined using the GNSS heighting method. The use of modern survey and mapping instruments based on satellite observations such as GNSS is more efficient in terms of time, effort, and cost compared to the accurate waterpass method. According to the Indonesian Geospatial Information Agency (BIG) it is stated that the application of geoid as a national Vertical Geospatial Reference System has an adequate and ideal category if the accuracy is higher than 15 cm. Recent studies have shown that it is possible to generate local geoid models with centimetre accuracy by utilizing airborne gravity data. We calculate free-air gravity anomaly data is calculated by processing airborne gravity and GNSS data using the Stokes Integral method on AGR software. Next a geoid model is created by calculating the contribution of three components, namely the long wave component represented by the EGM2008 global geoid data model, the shortwave component represented by the Shuttle Radar Topography Mission (SRTM) data and the medium wave component represented by the free-air gravity anomaly data. The geoid model validation was carried out using the geoid fitting method for geoid accuracy by calculating the difference between the gravimetric geoid and the geometric geoid and comparing it with the global geoid model EGM2008 degrees 2190. As a result, the total geoid model accuracy value was determined to be 49.4 cm on gravimetric geoid undulations with a standard deviation of 7.1 cm. Meanwhile, the results of the EGM2008 geoid undulation accuracy test at 2190 degrees resulted in an accuracy of 51.9 cm with a standard deviation of 9.9 cm. These results indicate that the local geoid model from airborne gravity measurement data produces a geoid model with a higher accuracy than the global geoid model EGM2008 degrees 2190. However, the accuracy of the resulting data is still below the BIG standard of 15 cm, so further research is needed to produce a geoid model which conforms to the standard.

scholarly journals Nonparametric Regression Model for Longitudinal Data with Mixed Truncated Spline and Fourier Series

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Made Ayu Dwi Octavanny ◽  
I. Nyoman Budiantara ◽  
Heri Kuswanto ◽  
Dyah Putri Rahmawati
Keyword(s):  
Fourier Series ◽  
Longitudinal Data ◽  
Nonparametric Regression ◽  
Simulated Data ◽  
Real Data ◽  
Least Square ◽  
Consistent Finding ◽  
Weighted Least Square ◽  
Stage Estimation

Existing literature in nonparametric regression has established a model that only applies one estimator to all predictors. This study is aimed at developing a mixed truncated spline and Fourier series model in nonparametric regression for longitudinal data. The mixed estimator is obtained by solving the two-stage estimation, consisting of a penalized weighted least square (PWLS) and weighted least square (WLS) optimization. To demonstrate the performance of the proposed method, simulation and real data are provided. The results of the simulated data and case study show a consistent finding.

scholarly journals Correcting airborne gravity data for overburden thickness: a case study from the Nechako interior plateau, British Columbia

2019 ◽  
Vol 56 (5) ◽  
pp. 483-492 ◽  
Author(s):  
Raymond M. Caron ◽  
Claire Samson ◽  
Martin Bates ◽  
Michel Chouteau
Keyword(s):  
British Columbia ◽  
Gravity Data ◽  
Random Noise ◽  
Airborne Gravity ◽  
Bedrock Topography ◽  
Transient Electromagnetic ◽  
Overburden Thickness ◽  
Line Spacing ◽  
Airborne Survey

Large areas of bedrock in Canada, such as in the interior plateau of British Columbia, are covered by a thick glacial overburden. Lateral variations in overburden thickness can create spurious anomalies in gravity data. These anomalies can be of a size and amplitude similar to those associated with mineral bodies and can be mistaken for them. A methodology is introduced that corrects gravity data for changes in overburden thickness through the use of a bedrock topography map created by integrating information from a helicopter transient electromagnetic survey with geological survey data, well water data, and gravel pit locations. The approach is tested for a 68 km × 38 km area in the prospective Nechako interior plateau of British Columbia, Canada. The methodology extends the traditional Bouguer corrections by taking into account the gravitational contribution of the overburden. Results show that the capability of an airborne survey to detect a change in overburden thickness depends primarily on survey line spacing and to a lesser extent on the level of random noise in the gravity data. The bedrock topography correction has the capability of removing the gravitational attraction of overburden for the purpose of revealing, through interpretation, geological structures in the gravity data that originate from the bedrock and are otherwise concealed.

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