scholarly journals Joint analysis of selected GRACE monthly spherical harmonic solutions and monthly MASCON solutions

2021 ◽  
Vol 51 (1) ◽  
pp. 47-61
Author(s):  
Adam NOVÁK ◽  
Juraj JANÁK ◽  
Barbora KOREKÁČOVÁ
Keyword(s):  
Gravity Field ◽  
Spherical Harmonic ◽  
Statistical Significance ◽  
Detailed Comparison ◽  
Joint Analysis ◽  
Satellite Mission ◽  
Science Data ◽  
Gravity Field Model ◽  
Global Gravity ◽  
Gravity Field Models

Study presented in this paper is focused on comparison and statistical assessment of differences between the selected Level 2 products of the satellite mission Gravity Recovery and Climate Experiment (GRACE). Global monthly gravity field models in terms of spherical harmonic coefficients produced by three institutes of GRACE Science Data System are compared with the partially independent MASCON global gravity field model. Detailed comparison and statistical analysis of differences is performed in 5 selected river basins: Amazon, Congo, Danube, Yenisei and Lena. For each spherical harmonic solution, 8 different filtrations available at International Center for Global Gravity Field Models (ICGEM) are tested over the time span from April 2002 to July 2016. Fischer test at two significance levels 10% and 5% has been performed in order to qualify the statistical significance between the particular solutions.

scholarly journals Sensitivity of Lageos Orbits to Global Gravity Field Models

2012 ◽  
Vol 47 (2) ◽  
pp. 47-65 ◽  
Author(s):  
K. Sośnica ◽  
D. Thaller ◽  
A. Jäggi ◽  
R. Dach ◽  
G. Beutler
Keyword(s):  
Gravity Field ◽  
Orbit Determination ◽  
Measurement Techniques ◽  
Precise Orbit Determination ◽  
Satellite Orbits ◽  
Gravity Field Model ◽  
Global Gravity ◽  
The Impact ◽  
Gravity Field Models

Sensitivity of Lageos Orbits to Global Gravity Field ModelsPrecise orbit determination is an essential task when analyzing SLR data. The quality of the satellite orbits strongly depends on the models used for dynamic orbit determination. The global gravity field model used is one of the crucial elements, which has a significant influence on the satellite orbit and its accuracy. We study the impact of different gravity field models on the determination of the LAGEOS-1 and -2 orbits for data of the year 2008. Eleven gravity field models are compared, namely JGM3 and EGM96 based mainly on SLR, terrestrial and altimetry data, AIUB-CHAMP03S based uniquely on GPS-measurements made by CHAMP, AIUB-GRACE03S, ITG-GRACE2010 based on GRACE data, and the combined gravity field models based on different measurement techniques, such as EGM2008, EIGEN-GL04C, EIGEN51C, GOCO02S, GO-CONS-2-DIR-R2, AIUB-SST. The gravity field models are validated using the RMS of the observation residuals of 7-day LAGEOS solutions. The study reveals that GRACE-based models have the smallest RMS values (i.e., about 7.15 mm), despite the fact that no SLR data were used to determine them. The coefficient C20is not always well estimated in GRACE-only models. There is a significant improvement of the gravity field models based on CHAMP, GRACE and GOCE w.r.t. models of the pre-CHAMP era. The LAGEOS orbits are particularly sensitive to the long wavelength part of the gravity fields. Differences of the estimated orbits due to different gravity field models are noticeable up to degree and order of about 30. The RMS of residuals improves from about 40 mm for degree 8, to about 7 mm for the solutions up to degrees 14 and higher. The quality of the predicted orbits is studied, as well.

MASCON versus spherical harmonic solutions to global monthly time varying gravity field

2020 ◽  
Author(s):  
Juraj Janák ◽  
Adam Novák ◽  
Barbora Korekáčová
Keyword(s):  
Gravity Field ◽  
Spherical Harmonic ◽  
Polar Region ◽  
Field Model ◽  
River Basins ◽  
Spherical Harmonic Analysis ◽  
Time Varying ◽  
Gravity Field Model ◽  
Gravity Field Models ◽  
Research Centres

<p>Satellite missions Gravity Field and Climate Experiment (GRACE) and its successor (GRACE-FO) plays very important role in nowadays research in geodesy, geophysics, hydrology, oceanography, glaciology and climatology. Various research centres adopted different procedures for processing the GRACE/GRACE-FO measurements in order to get the main final product – the global monthly gravity field model. Until now there have been developed and published two fundamentally different approaches to this problem. The first is well-known approach of spherical harmonic analysis and the second is more recent and more direct approach called in literature MASCON (Mass Concentration). The purpose of this contribution is to compare existing MASCON global monthly gravity field models with the selected models based on spherical harmonic approach. Comparison is performed in selected river basins and also in selected polar region. Chosen river basins differ both in size and seasonal changes of continental water storage to cover more situations. Comparison of different filtered versions of spherical harmonic solutions (DDK1 – DDK7) with MASCON solution is also performed in one of the analysed river basins. Differences are analysed and advantages and drawbacks of two approaches and of particular models are discussed.</p>

scholarly journals Validation of GOCE global gravity field models using terrestrial gravity data in Norway

2012 ◽  
Vol 2 (2) ◽  
pp. 134-143 ◽  
Author(s):  
M. Šprlák ◽  
C. Gerlach ◽  
B. Pettersen
Keyword(s):  
Harmonic Analysis ◽  
Gravity Field ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Gravity Field Model ◽  
Terrestrial Gravity ◽  
Free Air ◽  
Global Gravity ◽  
Free Air Gravity ◽  
Gravity Field Models

Validation of GOCE global gravity field models using terrestrial gravity data in NorwayThe GOCE (Gravity field and steady-state Ocean Circulation Explorer) satellite gravity gradiometry mission maps the Earth's gravity field. Harmonic analysis of GOCE observations provides a global gravity field model (GGFM). Three theoretical strategies, namely the direct, the space-wise and the time-wise approach, have been proposed for GOCE harmonic analysis. Based on these three methods, several GGFMs have been provided to the user community by ESA. Thereby different releases are derived from different periods of GOCE observations and some of the models are based on combinations with other sources of gravity field information. Due to the multitude of GOCE GGFMs, validation against independent data is a crucial task for the quality description of the different models.In this study, GOCE GGFMs from three releases are validated with respect to terrestrial free-air gravity anomalies in Norway. The spectral enhancement method is applied to avoid spectral inconsistency between the terrestrial and the GOCE free-air gravity anomalies.The results indicate that the time-wise approach is a reliable harmonic analysis procedure in all three releases of GOCE models. The space-wise approach, available in two releases, provides similar results as the time-wise approach. The direct approach seems to be highly affected by a-priori information.

scholarly journals The combined global gravity field model XGM2019e

2020 ◽  
Vol 94 (7) ◽  
Author(s):  
P. Zingerle ◽  
R. Pail ◽  
T. Gruber ◽  
X. Oikonomidou
Keyword(s):  
Gravity Field ◽  
Field Model ◽  
Gravity Field Model ◽  
Global Gravity ◽  
Global Gravity Field Model

scholarly journals Evaluation of Gravity Data Derived from Global Gravity Field Models Using Terrestrial Gravity Data in Enugu State, Nigeria

2018 ◽  
Vol 8 (1) ◽  
pp. 145-153 ◽  
Author(s):  
O.I. Apeh ◽  
E.C. Moka ◽  
V.N. Uzodinma
Keyword(s):  
Gravity Field ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Mean Square ◽  
Bouguer Gravity ◽  
Bouguer Anomalies ◽  
The Earth ◽  
Global Gravity ◽  
Enugu State ◽  
Gravity Field Models

Abstract Spherical harmonic expansion is a commonly applied mathematical representation of the earth’s gravity field. This representation is implied by the potential coeffcients determined by using elements/parameters of the field observed on the surface of the earth and/or in space outside the earth in the spherical harmonic expansion of the field. International Centre for Gravity Earth Models (ICGEM) publishes, from time to time, Global Gravity Field Models (GGMs) that have been developed. These GGMs need evaluation with terrestrial data of different locations to ascertain their accuracy for application in those locations. In this study, Bouguer gravity anomalies derived from a total of eleven (11) recent GGMs, using sixty sample points, were evaluated by means of Root-Mean-Square difference and correlation coeficient. The Root-Mean-Square differences of the computed Bouguer anomalies from ICGEMwebsite compared to their positionally corresponding terrestrial Bouguer anomalies range from 9.530mgal to 37.113mgal. Additionally, the correlation coe_cients of the structure of the signal of the terrestrial and GGM-derived Bouguer anomalies range from 0.480 to 0.879. It was observed that GECO derived Bouguer gravity anomalies have the best signal structure relationship with the terrestrial data than the other ten GGMs. We also discovered that EIGEN-6C4 and GECO derived Bouguer anomalies have enormous potential to be used as supplements to the terrestrial Bouguer anomalies for Enugu State, Nigeria.

Gravity Field Estimation from GRACE Follow-On Data: Results from CSR Analyses

2020 ◽  
Author(s):  
Srinivas Bettadpur ◽  
Himanshu Save ◽  
Peter Nagel ◽  
Nadège Pie ◽  
Steven Poole ◽  
...  
Keyword(s):  
Gravity Field ◽  
Lessons Learned ◽  
System Component ◽  
Science Data ◽  
Orbit Plane ◽  
Flight Data ◽  
University Of Texas ◽  
Earth Gravity ◽  
Grace Data ◽  
Gravity Field Models

<p>At the time of presentation, nearly two years of flight data from the joint NASA/GFZ GRACE Folllow-On mission will have been collected. In this time, gravity field models have been produced using two independent inter-satellite tracking systems - the MWI and the LRI using radio and optical interferometry, respectively. The data have been analyzed over more than two complete cycles of the sun relative to the orbit plane, allowing a characterization of the environmental impacts on the flight data. Extended duration of analyses have also permitted an assessment of the GRACE-FO data relative to the corresponding GRACE data.</p><p>This poster presents the status and lessons learned from two years of estimation of Earth gravity field models from the GRACE-FO data at the science data system component at the University of Texas Center for Space Research.</p>

Simulated experiment of recovering gravity field from the observations of satellite’s frequency signal

2020 ◽  
Author(s):  
Xinyu Xu ◽  
Ziyu Shen ◽  
Wenbin Shen ◽  
Yongqi Zhao
Keyword(s):  
Gravity Field ◽  
Field Model ◽  
Reference Model ◽  
Satellite Orbit ◽  
The Other ◽  
Frequency Signal ◽  
Gravity Field Model ◽  
Simulated Experiment ◽  
The One ◽  
Gravity Field Models

<p><span>Recovering the gravity field with the satellite’s frequency signal might be an alternative measuring mode in the future when the accuracy of the onboard clock was good enough. On the one hand, we analyze the performance of recovering gravity field model from the gravitational potentials with different accuracies on different satellite altitudes (from 200 km to 350 km) based on semi-analytical (SA) method. On the other hand, we analyze the performance based on the numerical analysis. First, the gravitational potentials along the satellite orbit are computed from the clock observations based on the method of satellite’s frequency signal with the accuracies of 10<sup>-16</sup> and 10<sup>-18</sup>s. Then, based on the derived gravitational potentials, we recovered the gravity field models up to degree and order 200 (corresponding to 100 km spatial resolution). At last, the errors of recovered models are validated by comparing with the reference model.</span></p>

Fitting the GPS/Leveling Quasi-Geoid Using Bayesian-Regulation BP Neural Network

2011 ◽  
Vol 90-93 ◽  
pp. 2903-2906
Author(s):  
Lei Song ◽  
Xiao Qing Hu
Keyword(s):  
Neural Network ◽  
Gravity Field ◽  
Bp Neural Network ◽  
Field Model ◽  
Gravity Field Model ◽  
Global Gravity ◽  
Fitting In ◽  
Gps Leveling ◽  
Global Gravity Field Model

The 2.5′×2.5′resolution local quasi-geoid is calculated using the global gravity field model and GPS/leveling data of region which points spacing is about 10km with the Bayesian- regulation BP neural network in this paper. The inner and outer precision of quasi-geoid are both superior 0.05m.The result indicat that the Bayesian regulation BP neural network could improve the precision of fitting and restrain the over-fitting in fitting. The region quasi-geoid excelled than 0.05m can be computed using the global gravity field model and about 10km baseline GPS/leveling data in smoothness region.

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