Trend Analysis and Fast Fourier Interpretation of Marine Gravity Measurements

1975 ◽  
Author(s):  
William C. Pearson ◽  
C.R.B. Lister
Keyword(s):  
Trend Analysis ◽  
Marine Gravity ◽  
Gravity Measurements

A comparison between sea-bottom gravity and satellite altimeter-derived gravity in coastal environments: A case study of the Gulf of Manfredonia (SW Adriatic Sea)

2021 ◽  
Author(s):  
Luigi Sante Zampa ◽  
Emanuele Lodolo ◽  
Nicola Creati ◽  
Martina Busetti ◽  
Gianni Madrussani ◽  
...  
Keyword(s):  
Gravity Field ◽  
Satellite Altimetry ◽  
Adriatic Sea ◽  
Gravity Anomalies ◽  
Satellite Altimeter ◽  
Sea Bottom ◽  
Marine Gravity ◽  
Gravity Measurements ◽  
Near Shore ◽  
Italian Coasts

<p>In this study, we present a comparative analysis between two types of gravity data used in geophysical applications: satellite altimeter-derived gravity and sea-bottom gravity.</p><p>It is largely known that the marine gravity field derived from satellite altimetry in coastal areas is generally biased by signals back-scattered from the nearby land. As a result, the derived gravity anomalies are mostly unreliable for geophysical and geological interpretations of near-shore environments.</p><p>To quantify the errors generated by the land-reflected signals and to verify the goodness of the geologic models inferred from gravity, we compared two different altimetry models with sea-bottom gravity measurements acquired along the Italian coasts from the early 50s to the late 80s.</p><p>We focused on the Gulf of Manfredonia, located in the SE sector of the Adriatic Sea, where: (i) two different sea-bottom gravity surveys have been conducted over the years, (ii) the bathymetry is particularly flat, and (iii) seismic data revealed a prominent carbonate ridge covered by hundreds of meters of Oligocene-Quaternary sediments.</p><p>Gravity field derivatives have been used to enhance both: (i) deep geological contacts, and (ii) coastal noise. The analyses outlined a “ringing-noise effect” which causes the altimeter signal degradation up to 17 km from the coast.</p><p>Differences between the observed gravity and the gravity calculated from a geological model constrained by seismic, showed that all datasets register approximately the same patterns, associated with the Gondola Fault Zone, a major structural discontinuity traversing roughly E-W the investigated area.</p><p>This study highlights the importance of implementing gravity anomalies derived from satellite-altimetry with high-resolution near-shore data, such as the sea-bottom gravity measurements available around the Italian coasts. Such analysis may have significant applications in studying the link between onshore and offshore geological structures in transitional areas.</p>

On the accuracy of marine gravity measurements

1988 ◽  
Vol 93 (B1) ◽  
pp. 393-413 ◽  
Author(s):  
Pål Wessel ◽  
Anthony B. Watts
Keyword(s):  
Marine Gravity ◽  
Gravity Measurements

scholarly journals Regional Seafloor Topography by Extended Kalman Filtering of Marine Gravity Data without Ship-Track Information

2021 ◽  
Vol 14 (1) ◽  
pp. 169
Author(s):  
Lucía Seoane ◽  
Guillaume Ramillien ◽  
Benjamin Beirens ◽  
José Darrozes ◽  
Didier Rouxel ◽  
...  
Keyword(s):  
Gravity Data ◽  
Geoid Height ◽  
Extended Kalman Filtering ◽  
Seafloor Topography ◽  
Single Beam ◽  
Beam Depth ◽  
Marine Gravity ◽  
Gravity Measurements ◽  
Polynomial Series ◽  
Free Air Anomaly

An iterative Extended Kalman Filter (EKF) approach is proposed to recover a regional set of topographic heights composing an undersea volcanic mount by the successive combination of large numbers of gravity measurements at sea surface using altimetry satellite-derived grids and taking the error uncertainties into account. The integration of the non-linear Newtonian operators versus the radial and angular distances (and its first derivatives) enables the estimation process to accelerate and requires only few iterations, instead of summing Legendre polynomial series or using noise-degraded 2D-FFT decomposition. To show the effectiveness of the EKF approach, we apply it to the real case of the bathymetry around the Great Meteor seamount in the Atlantic Ocean by combining only geoid height/free-air anomaly datasets and using ship-track soundings as reference for validation. Topography of the Great Meteor seamounts structures are well-reconstructed, especially when regional compensation is considered. Best solution gives a RMS equal to 400 m with respect to the single beam depth observations and it is comparable to RMS obtained for ETOPO1 of about 365 m. Larger discrepancies are located in the seamount flanks due to missing high-resolution information for gradients. This approach can improve the knowledge of seafloor topography in regions where few echo-sounder measurements are available.

Near‐real time reduction of shipboard gravity using Kalman‐filtered GPS measurements

Geophysics ◽  
1991 ◽  
Vol 56 (12) ◽  
pp. 1971-1979 ◽  
Author(s):  
J. F. Genrich ◽  
J.-B. Minster
Keyword(s):  
Real Time ◽  
Impulse Response ◽  
Finite Impulse Response ◽  
Yield Data ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Marine Gravity ◽  
Gravity Measurements ◽  
Low Pass ◽  
Stabilized Platform

We have developed a Kalman filter to estimate accurate Eötvös corrections and horizontal ship accelerations from Global Positioning System (GPS) fixes. High‐resolution shipboard gravity measurements are obtained with a newly designed, linear phase, Finite Impulse Response (FIR) low‐pass filter. Both filters are combined to yield accurate, near‐real time, Eötvös‐corrected underway gravity estimates. Error ranges that reflect uncertainty in navigation for these estimates are calculated from autocovariances of Kalman velocity estimates by means of variance propagation expressions for time‐invariant linear digital filters. Estimates of horizontal ship acceleration are combined with a simplified instrument impulse response model in an attempt to remove transient noise from the gravimeter output. We apply the technique to data collected by two shipboard gravimeters, a LaCoste & Romberg Model S Air‐Sea Gravity Meter and a Bell Aerospace BGM-3 Marine Gravity Meter System, operated side‐by‐side on the Scripps R/V Thomas Washington during Leg 1 of the Roundabout expedition. In the absence of significant horizontal accelerations due to course or speed changes, both instruments yield data with good repeatability, characterized by rms differences of less than 1 mGal. Horizontal accelerations generate transient signals that cannot be modeled at present to an accuracy of better than 5 mGal. Difficulties in removing these transients are primarily due to insufficient quantitative knowledge of the response of the instrument, including the gyro‐stabilized platform. This can be determined analytically or empirically.

Dynamics and navigation of autonomous underwater vehicles for submarine gravity surveying

Geophysics ◽  
2013 ◽  
Vol 78 (3) ◽  
pp. G55-G68 ◽  
Author(s):  
James C. Kinsey ◽  
Maurice A. Tivey ◽  
Dana R. Yoerger
Keyword(s):  
Autonomous Underwater Vehicle ◽  
Gravity Data ◽  
Autonomous Underwater Vehicles ◽  
Free Water ◽  
Cost Effective ◽  
Marine Gravity ◽  
State Estimators ◽  
Gravity Measurements ◽  
Effective Option ◽  
Vertical Accelerations

We investigated the effect of autonomous underwater vehicle (AUV) dynamics and navigation on underway submarine gravimetry. Our research was motivated by the need to obtain spatially dense marine gravity measurements close to the source of subkilometer-scale geologic features in the shallow oceanic crust. Such measurements have been previously obtained, for instance, with piloted submarines and towed sleds; however, the high cost and, in the case of on-bottom measurements, poor spatial sampling preclude routine acquisition of these measurements. Continuous underway gravity surveys with AUVs is a compelling cost-effective option, but this method requires separating the AUV accelerations from the measured gravity. We show that AUVs with a large distance between the center of buoyancy and the center of gravity have lower vertical accelerations than torpedo-shaped AUVs and consequentially are better suited for underway gravity surveys. Furthermore state estimators, which combine sensor measurements and models of the vehicle’s motion, provide superior estimates of the vehicle’s vertical accelerations than methods used in previous underway submarine gravity surveys. We simulated the use of these navigation methods in detecting dike swarms at the East Pacific Rise. Analysis showed that we can shorten filters used in reducing gravity data and consequentially provide improved measurements of the free-water anomaly with a minimal detectable spatial wavelength approximately 65% lower than previously reported results.

Basement control of structures in the Mesozoic rocks in the Strait of Dover region, and its reflexion in certain features of the present land and submarine topography

1972 ◽  
Vol 272 (1221) ◽  
pp. 99-110 ◽  
Keyword(s):  
Site Investigation ◽  
Field Surveys ◽  
Marine Gravity ◽  
Gravity Measurements ◽  
History Of ◽  
Geophysical Investigations ◽  
Deep Boreholes ◽  
Geological Sciences ◽  
First Time ◽  
Review Current

The purpose of this paper is to review current information and opinions on the structures of the concealed Palaeozoic rocks of southeastern England and adjacent parts of northwestern Europe. The authors attempt a regional synthesis, which suggests that certain structural trends in these older rocks have been reactivated several times in the subsequent history of the area, and in some cases control the alinement of present-day surface features. We have drawn on the accumulated data of field surveys, deep boreholes and geophysical investigations carried out by the Institute of Geological Sciences, and also information obtained during the commercial search for coal and oil. The results of marine gravity measurements recently made by I.G.S. and the Admiralty in the eastern English Channel and southern North Sea are presented for the first time. Similarly, we are glad to include data from M r P. L. Rumsby’s recent analyses of fault trends in the Kent collieries, for the National Coal Board. Reference is also made to some of the results of the Channel Tunnel site investigation 1964 5 (Destombes & Shephard-Thorn 1971). Published literature and maps form the basis of our remarks on northern Europe, though we are grateful to Destombes for unpublished information on the Boulonnais.

scholarly journals The Effect of Measurement Preprocessing intheGravity-Aided Navigation

2021 ◽  
Author(s):  
Oleg Andreevich Stepanov ◽  
Aleksei Sergeevich Nosov
Keyword(s):  
Navigation Problem ◽  
One Dimensional ◽  
Preliminary Processing ◽  
Marine Gravity ◽  
Gravity Measurements

AbstractThe paper analyzes the effect of preliminary processing of gravity measurements on the accuracy of the marine gravity-aided navigation. The preliminary processing of the measurements is implemented in the filtering and smoothing modes. Obtained results are illustrated by a one-dimensional example of gravity-aided navigation problem.

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