scholarly journals Accuracy assessment of test flights using the Turnkey Airborne Gravity System over Alabama in 2008

2013 ◽  
Vol 3 (2) ◽  
pp. 136-142 ◽  
Author(s):  
Y.M. Wang ◽  
S. Preaux ◽  
T. Diehl ◽  
V. Childers ◽  
D. Roman ◽  
...  
Keyword(s):  
Gravity Data ◽  
Gravity Anomalies ◽  
Gravity Models ◽  
Surface Gravity ◽  
Airborne Gravity ◽  
National Geodetic Survey ◽  
The Mean ◽  
The Impact ◽  
Gravity System ◽  
Better Than

AbstractThe National Geodetic Survey (NGS) performed a few test flights using Micro-g’s Turnkey Airborne Gravity System (TAGS) at altitude of 1700, 6300 and 11000 meters over Alabama in 2008. The cross-track spacing was 10 km for the two lower flights and 5 km for the highest flight. The test flights not only provided important information regarding the precision and accuracy of the TAGS but also revealed the impact of flight altitudes and track spacing on the collected gravity data. The gravity anomalies at three altitudes were modeled using 3-dimensional Fourier series, then compared at the three altitudes. The agreement was excellent - the gravity anomalies agree with each other from 1.4 to 3.3 mGal RMS at the three altitudes. When the bias was removed, the agreement was improved to better than 1.1 mGal. On the ground (h =0), the three gravity models agree from 1.9 to 3.8 mGal RMS. After removing the mean, the agreement improved to better than 1.7 mGal. Similar results were obtained in comparison with recent surface gravity which was of sub-mGal accuracy. The overall agreement between the downward continued airborne gravity and the surface gravity was better than 1.7 mGal after removing the mean values.As expected, the flight altitude had a direct impact on accuracy of the values of gravity downward continued to the Earth’s surface. The comparisons with terrestrial gravity show that gravity collected at 11000 m is having an accuracy of ±3 mGal on the ground. This accuracy is slightly worse than the other two altitudes most probably due to smaller signal/noise ratios and larger downward continuation effects. The RMS values of differences between the downward continued airborne gravity at altitude 1700 and 6300 meters and the surface gravity are 2.0 and 1.6 mGals, respectively. Based on these comparisons, airborne gravity data collected at altitudes below 6300 meters should result in accuracy better than ±2 mGals on the ground. Note, however, that the test area is flat and the accuracy of airborne gravity would likely be worse in more rugged mountainous regions.

Study on Filtering Methods of Airborne Gravity

2013 ◽  
Vol 333-335 ◽  
pp. 516-521
Author(s):  
Wei Zhou ◽  
Ti Jing Cai
Keyword(s):  
Impulse Response ◽  
Finite Impulse Response ◽  
Gravity Data ◽  
Low Frequency ◽  
Gravity Anomalies ◽  
Window Function ◽  
Airborne Gravity ◽  
Infinite Impulse Response ◽  
Kalman Smoothing ◽  
Better Than

There are a great number of high-frequency and low-frequency noises in the airborne gravity data, so the filtering technology is needed to pick up the weak gravity anomaly. Based on the current filtering methods in airborne gravity data processing: butterworth infinite impulse response(IIR) filtering, window function finite impulse response(FIR) filtering and Kalman smoothing, several methods were compared and studied for the measured airborne gravity data, and the accuracies of extracted gravity anomalies were presented. Results show that the accuracy of Kalman smoothing is better than that of the combined filtering with butterworth IIR and window function FIR.

The gravity field over the Ungava Bay region from satellite altimetry and new land-based data: implications for the geology of the area

1999 ◽  
Vol 36 (1) ◽  
pp. 75-89 ◽  
Author(s):  
Hamid Telmat ◽  
Jean-Claude Mareschal ◽  
Clément Gariépy
Keyword(s):  
Satellite Altimetry ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Gravity Models ◽  
Crustal Thickening ◽  
Seismic Line ◽  
Crustal Thinning ◽  
Gravity Measurements ◽  
George River ◽  
Superior Craton

Gravity data were obtained along two transects on the southern coast of Ungava Bay, which provide continuous gravity coverage between Leaf Bay and George River. The transects and the derived gravity profiles extend from the Superior craton to the Rae Province across the New Quebec Orogen (NQO). Interpretation of the transect along the southwestern coast of Ungava Bay suggests crustal thickening beneath the NQO and crustal thinning beneath the Kuujjuaq Terrane, east of the NQO. Two alternative interpretations are proposed for the transect along the southeastern coast of the bay. The first model shows crustal thickening beneath the George River Shear Zone (GRSZ) and two shallow bodies correlated with the northern extensions of the GRSZ and the De Pas batholith. The second model shows constant crustal thickness and bodies more deeply rooted than in the first model. The gravity models are consistent with the easterly dipping reflections imaged along a Lithoprobe seismic line crossing Ungava Bay and suggest westward thrusting of the Rae Province over the NQO. Because no gravity data have been collected in Ungava Bay, satellite altimetry data have been used as a means to fill the gap in data collected at sea. The satellite-derived gravity data and standard Bouguer gravity data were combined in a composite map for the Ungava Bay region. The new land-based gravity measurements were used to verify and calibrate the satellite data and to ensure that offshore gravity anomalies merge with those determined by the land surveys in a reasonable fashion. Three parallel east-west gravity profiles were extracted: across Ungava Bay (59.9°N), on the southern shore of the bay (58.5°N), and onshore ~200 km south of Ungava Bay (57.1°N). The gravity signature of some major structures, such as the GRSZ, can be identified on each profile.

The experimental geoid 2020 – the first joint geoid model for the North American and Pacific Geopotential Datum 

2021 ◽  
Author(s):  
Yan Ming Wang ◽  
Xiaopeng Li ◽  
Kevin Ahlgren ◽  
Jordan Krcmaric ◽  
Ryan Hardy ◽  
...  
Keyword(s):  
North American ◽  
Gravity Data ◽  
The United States ◽  
Geodetic Survey ◽  
Airborne Gravity ◽  
Data Sets ◽  
National Geodetic Survey ◽  
Geoid Model ◽  
Satellite Gravity ◽  
The North

<p>For the upcoming North American-Pacific Geopotential Datum of 2022, the National Geodetic Survey (NGS), the Canadian Geodetic Survey (CGS) and the National Institute of Statistics and Geography of Mexico (INEGI) computed the first joint experimental gravimetric geoid model (xGEOID) on 1’x1’ grids that covers a region bordered by latitude 0 to 85 degree, longitude 180 to 350 degree east. xGEOID20 models are computed using terrestrial gravity data, the latest satellite gravity model GOCO06S, altimetric gravity data DTU15, and an additional nine airborne gravity blocks of the GRAV-D project, for a total of 63 blocks. In addition, a digital elevation model in a 3” grid was produced by combining MERIT, TanDEM-X, and USGS-NED and used for the topographic/gravimetric reductions. The geoid models computed from the height anomalies (NGS) and from the Helmert-Stokes scheme (CGS) were combined using two different weighting schemes, then evaluated against the independent GPS/leveling data sets. The models perform in a very similar way, and the geoid comparisons with the most accurate Geoid Slope Validation Surveys (GSVS) from 2011, 2014 and 2017 indicate that the relative geoid accuracy could be around 1-2 cm baseline lengths up to 300 km for these GSVS lines in the United States. The xGEOID20 A/B models were selected from the combined models based on the validation results. The geoid accuracies were also estimated using the forward modeling.</p>

Coastal Gravity Anomalies from Retracked Geosat/GM Altimetry: Improvement, Limitation and the Role of Airborne Gravity Data

2006 ◽  
Vol 80 (4) ◽  
pp. 204-216 ◽  
Author(s):  
Cheinway Hwang ◽  
Jinyun Guo ◽  
Xiaoli Deng ◽  
Hsin-Ying Hsu ◽  
Yuting Liu
Keyword(s):  
Gravity Data ◽  
Gravity Anomalies ◽  
Airborne Gravity

The Origin of Lunar Mascon Basins

Science ◽  
2013 ◽  
Vol 340 (6140) ◽  
pp. 1552-1555 ◽  
Author(s):  
H. J. Melosh ◽  
Andrew M. Freed ◽  
Brandon C. Johnson ◽  
David M. Blair ◽  
Jeffrey C. Andrews-Hanna ◽  
...  
Keyword(s):  
Gravity Data ◽  
Gravity Anomalies ◽  
Element Model ◽  
Isostatic Adjustment ◽  
Melt Pool ◽  
Free Air ◽  
Free Air Gravity ◽  
Bull's Eye ◽  
Gravity Recovery ◽  
The Impact

High-resolution gravity data from the Gravity Recovery and Interior Laboratory spacecraft have clarified the origin of lunar mass concentrations (mascons). Free-air gravity anomalies over lunar impact basins display bull’s-eye patterns consisting of a central positive (mascon) anomaly, a surrounding negative collar, and a positive outer annulus. We show that this pattern results from impact basin excavation and collapse followed by isostatic adjustment and cooling and contraction of a voluminous melt pool. We used a hydrocode to simulate the impact and a self-consistent finite-element model to simulate the subsequent viscoelastic relaxation and cooling. The primary parameters controlling the modeled gravity signatures of mascon basins are the impactor energy, the lunar thermal gradient at the time of impact, the crustal thickness, and the extent of volcanic fill.

scholarly journals GRAVITY ANOMALY ASSESSMENT USING GGMS AND AIRBORNE GRAVITY DATA TOWARDS BATHYMETRY ESTIMATION

2016 ◽  
Vol XLII-4/W1 ◽  
pp. 287-297
Author(s):  
A. Tugi ◽  
A. H. M. Din ◽  
K. M. Omar ◽  
A. S. Mardi ◽  
Z. A. M. Som ◽  
...  
Keyword(s):  
Gravity Anomaly ◽  
Gravity Field ◽  
Ocean Circulation ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Airborne Gravity ◽  
Satellite Gravity ◽  
Earth’S Gravity Field ◽  
Explorer Mission ◽  
Satellite Gravity Missions

The Earth’s potential information is important for exploration of the Earth’s gravity field. The techniques of measuring the Earth’s gravity using the terrestrial and ship borne technique are time consuming and have limitation on the vast area. With the space-based measuring technique, these limitations can be overcome. The satellite gravity missions such as Challenging Mini-satellite Payload (CHAMP), Gravity Recovery and Climate Experiment (GRACE), and Gravity-Field and Steady-State Ocean Circulation Explorer Mission (GOCE) has introduced a better way in providing the information on the Earth’s gravity field. From these satellite gravity missions, the Global Geopotential Models (GGMs) has been produced from the spherical harmonics coefficient data type. The information of the gravity anomaly can be used to predict the bathymetry because the gravity anomaly and bathymetry have relationships between each other. There are many GGMs that have been published and each of the models gives a different value of the Earth’s gravity field information. Therefore, this study is conducted to assess the most reliable GGM for the Malaysian Seas. This study covered the area of the marine area on the South China Sea at Sabah extent. Seven GGMs have been selected from the three satellite gravity missions. The gravity anomalies derived from the GGMs are compared with the airborne gravity anomaly, in order to figure out the correlation (R<sup>2</sup>) and the root mean square error (RMSE) of the data. From these assessments, the most suitable GGMs for the study area is GOCE model, GO_CONS_GCF_2_TIMR4 with the R<sup>2</sup> and RMSE value of 0.7899 and 9.886 mGal, respectively. This selected model will be used in the estimating the bathymetry for Malaysian Seas in future.

scholarly journals GROUNDNUT GROWTH AND YIELD RESPONSES TO CALCIUM AND PHOSPHOROUS FERTILIZATION

2021 ◽  
Vol 9 (4) ◽  
pp. 688-693
Author(s):  
Razan Malla ◽  
◽  
Saraswoti Kandel ◽  
Bisheswar Prasasd Yadav ◽  
Santosh Rasaily ◽  
...  
Keyword(s):  
Yield Components ◽  
Fertilizer Application ◽  
Growth And Yield ◽  
Pod Yield ◽  
Arachis Hypogaea L ◽  
Production Quantity ◽  
The Mean ◽  
Yield Responses ◽  
The Impact ◽  
Better Than

An experiment was conducted in factorial design with three replications in Nawalpur, Sarlahi, Nepal in 2018 and 2019 to investigate the impact of calcium and phosphorous application on yield and yield components of groundnut (Arachis hypogaea L.). Baidehi variety of groundnut was used. Calcium concentrations in three levels (0, 110, and 165 kg ha-1 from Gypsum) and phosphorous rates in three levels (0, 25, and 50 kg ha-1 from SSP) were used in this study. The application of calcium had a major impact on pod production, quantity of filled pods, and hundred seed weight, with 165 kg ha-1 calcium from gypsum performing significantly better than the others. The highest pod yield (2006 and 2477 kg ha-1) was obtained from calcium 165 kg ha-1 in 2018 and 2019 respectively. Calcium application (165 kg ha-1) increased the mean pod yield by 24% compared to the control. Control plots resulted in more than 13% empty pods (pops) compared to when applied with 165 kg Ca ha-1. Phosphorus was rich in the inherent soil leading to no significant effect on the yield components. According to the findings of this research, efficient fertilizer application, especially calcium and phosphorus, is critical for groundnut nutrition and pod filling.

scholarly journals Euclid: The importance of galaxy clustering and weak lensing cross-correlations within the photometric Euclid survey

2020 ◽  
Vol 643 ◽  
pp. A70 ◽  
Author(s):  
I. Tutusaus ◽  
M. Martinelli ◽  
V. F. Cardone ◽  
S. Camera ◽  
S. Yahia-Cherif ◽  
...  
Keyword(s):  
Gravity Models ◽  
Weak Lensing ◽  
Matrix Formalism ◽  
Photometric Redshift ◽  
Bias Model ◽  
Systematic Effects ◽  
The Mean ◽  
Galaxy Bias ◽  
The Impact ◽  
Parameter Constraints

Context. The data from the Euclid mission will enable the measurement of the angular positions and weak lensing shapes of over a billion galaxies, with their photometric redshifts obtained together with ground-based observations. This large dataset, with well-controlled systematic effects, will allow for cosmological analyses using the angular clustering of galaxies (GCph) and cosmic shear (WL). For Euclid, these two cosmological probes will not be independent because they will probe the same volume of the Universe. The cross-correlation (XC) between these probes can tighten constraints and is therefore important to quantify their impact for Euclid. Aims. In this study, we therefore extend the recently published Euclid forecasts by carefully quantifying the impact of XC not only on the final parameter constraints for different cosmological models, but also on the nuisance parameters. In particular, we aim to decipher the amount of additional information that XC can provide for parameters encoding systematic effects, such as galaxy bias, intrinsic alignments (IAs), and knowledge of the redshift distributions. Methods. We follow the Fisher matrix formalism and make use of previously validated codes. We also investigate a different galaxy bias model, which was obtained from the Flagship simulation, and additional photometric-redshift uncertainties; we also elucidate the impact of including the XC terms on constraining these latter. Results. Starting with a baseline model, we show that the XC terms reduce the uncertainties on galaxy bias by ∼17% and the uncertainties on IA by a factor of about four. The XC terms also help in constraining the γ parameter for minimal modified gravity models. Concerning galaxy bias, we observe that the role of the XC terms on the final parameter constraints is qualitatively the same irrespective of the specific galaxy-bias model used. For IA, we show that the XC terms can help in distinguishing between different models, and that if IA terms are neglected then this can lead to significant biases on the cosmological parameters. Finally, we show that the XC terms can lead to a better determination of the mean of the photometric galaxy distributions. Conclusions. We find that the XC between GCph and WL within the Euclid survey is necessary to extract the full information content from the data in future analyses. These terms help in better constraining the cosmological model, and also lead to a better understanding of the systematic effects that contaminate these probes. Furthermore, we find that XC significantly helps in constraining the mean of the photometric-redshift distributions, but, at the same time, it requires more precise knowledge of this mean with respect to single probes in order not to degrade the final “figure of merit”.

Using isostatic gravity anomalies from spherical harmonic models and elastic plate compensation to interpret the lithosphere of the Bolivian Andes

Geophysics ◽  
2013 ◽  
Vol 78 (3) ◽  
pp. G41-G53 ◽  
Author(s):  
Christopher Jekeli ◽  
Hyo Jin Yang ◽  
Kevin Ahlgren
Keyword(s):  
Spherical Harmonic ◽  
Flexural Rigidity ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Surface Gravity ◽  
Bolivian Andes ◽  
Isostatic Gravity Anomalies ◽  
Isostatic Gravity ◽  
Spherical Harmonic Models ◽  
Surface Gravity Data

We have determined for the Bolivian Andes that the new global gravity models derived from the Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite mission may be used directly to study lithospheric structure. Toward this end, we have formulated Bouguer and isostatic gravity anomalies in spherical approximation, rather than in the usual planar approach, using spherical harmonic series consistent with the satellite-derived gravitational models. From the approximate equivalency of topographic masses and surface density layers using the Helmert condensation method we further derived and used isotropic transfer relations between the spherical spectra of topographic loads and elastic spherical shell deflections, where the Airy isostatic compensation is the special case of no flexural rigidity. A numerical comparison of these spherical harmonic models to conventional three-dimensional modeling based on topographic data and newly acquired surface gravity data in Bolivia confirmed their suitability for lithospheric interpretation. Specifically, the relatively high and uniform resolution of the satellite gravitational model (better than 83 km) produces detailed maps of the isostatic anomaly that clearly delineate the flexure of the Brazilian shield that is thrust under the Sub-Andes. Inferred values of the thickness of Airy-type roots and the flexural rigidity of the elastic lithosphere agree reasonably with published results based on seismic and surface gravity data. In addition, a local minimum in the flexural rigidity is evident at the sharp bend of the eastern margins of the Sub-Andes in Bolivia. This feature is consistent with earlier theories for counter rotations about a vertical axis at this minimum, associated with the confluence of the subducted Nazca plate and the Brazilian craton. The GOCE model thus generates high-resolution isostatic anomaly maps that offer additional structural detail not seen as clearly from previous seismic and gravity investigations in this region.

Geophysical constraints on the nature of the Highland Boundary Fault Zone in western Scotland

1992 ◽  
Vol 129 (4) ◽  
pp. 411-419 ◽  
Author(s):  
M. C. Dentith ◽  
A. Trench ◽  
B. J. Bluck
Keyword(s):  
Fault Zone ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Thrust Fault ◽  
Gravity Models ◽  
Reverse Fault ◽  
Red Sandstone ◽  
Boundary Fault ◽  
Models Of Gravity ◽  
Surface Geology

AbstractPreviously published models of gravity anomalies across the Highland Boundary Fault in western Scotland interpret this structure as a high-angle reverse fault. These gravity anomalies have been re-interpreted in the light of more extensive gravity data now available, and new density data from the Highland Border Complex. The new data suggest that earlier interpretations have overestimated the fault anomaly and used over-simplified density models. New gravity models of the Highland Boundary Fault Zone are presented which show that the interface between the Dalradian and Highland Border Complex dips to the northwest at an angle of about 20°. We interpret the contact between these two formations as a thrust fault. The interface between the Highland Border Complex and the Lower Old Red Sandstone is shown to be vertical as suggested by surface geology, with the latter rocks a few hundred metres thick.

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