Marine gravity

Dehlinger, Peter

doi:10.1029/eo052i003piu021

Cited by 6 publications

(7 citation statements)

References 17 publications

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“…Maximum Eötvös corrections arise when a vessel is heading due east along the equator. A vessel cruising at the upper velocity limit should encounter Eötvös corrections no larger than 150 mGal [ Dehlinger , 1978]. …”

Section: Limits On Geophysical Observationsmentioning

confidence: 99%

Improving the quality of marine geophysical track line data: Along‐track analysis

Chandler¹,

Wessel²

2008

J. Geophys. Res.

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[1] We have examined 4918 track line geophysics cruises archived at the U.S. National Geophysical Data Center (NGDC) using comprehensive error checking methods. Each cruise was checked for observation outliers, excessive gradients, metadata consistency, and general agreement with satellite altimetry-derived gravity and predicted bathymetry grids. Thresholds for error checking were determined empirically through inspection of histograms for all geophysical values, gradients, and differences with gridded data sampled along ship tracks. Robust regression was used to detect systematic scale and offset errors found by comparing ship bathymetry and free-air anomalies to the corresponding values from global grids. We found many recurring error types in the NGDC archive, including poor navigation, inappropriately scaled or offset data, excessive gradients, and extended offsets in depth and gravity when compared to global grids. While $5-10% of bathymetry and free-air gravity records fail our conservative tests, residual magnetic errors may exceed twice this proportion. These errors hinder the effective use of the data and may lead to mistakes in interpretation. To enable the removal of gross errors without over-writing original cruise data, we developed an errata system that concisely reports all errors encountered in a cruise. With such errata files, scientists may share cruise corrections, thereby preventing redundant processing. We have implemented these quality control methods in the modified MGD77 supplement to the Generic Mapping Tools software suite.Citation: Chandler, M. T., and P. Wessel (2008), Improving the quality of marine geophysical track line data: Along-track analysis,

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Section: Limits On Geophysical Observationsmentioning

confidence: 99%

Improving the quality of marine geophysical track line data: Along‐track analysis

Chandler¹,

Wessel²

2008

J. Geophys. Res.

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“…In contrast, our study of 1,807 tracks (537,246 COEs) finds a 34% reduction in COE standard deviation from 44.87 mGal to 29.69 mGal. Whereas the Wessel and Watts [1988] analysis vertically adjusted all but 72 of these tracks and additionally scaled 146 tracks to account for gravimeter drift [e.g., Dehlinger , 1978], our methods provide a comparable data quality improvement while scaling only 18 tracks by 10 or 0.1, removing constant gravity offsets from 15 surveys (FAA rows with +/− factors in Table 2) and by disregarding 63 tracks (Table 4) as containing erroneous data. Note that these COE values are reduced simply by applying along‐track corrections; no further modeling of systematic COE was done.…”

Section: Discussionmentioning

confidence: 99%

Errata‐based correction of marine geophysical trackline data

Chandler

Wessel

2012

Geochem Geophys Geosyst

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[1] We announce the completion of 5,230 errata correction tables which remove extreme, obvious errors from the National Geophysical Data Center's marine geophysical trackline archive. Along with a range of error types correctable using along-track analysis, we determined that $62% of gravity surveys omit raw measurements and that $89% of magnetic anomalies are outdated and require recomputing. These errata tables reduce median global crossovers from 27.3 m to 24.0 m (bathymetry), 81.6 nT to 29.6 nT (magnetic anomalies) and 6.0 mGal to 4.4 mGal (free air gravity). We consider these methods gentler and more fundamental than the predominant crossover approach in that along-track corrections affect only data flagged as erroneous by a reviewer; the vast majority of data are left unchanged. Removal of obvious errors is an important initial step that should precede crossover analysis, interpolation, and gridding, thereby strengthening the scientific analysis.Components: 9300 words, 9 figures, 4 tables.

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“…A density distribution of the earth was proposed by Bullen in 1963 and the mean density of the layer is 2.9xld kg/m3 as the depth is less than lo00 m (Dehlinger, 1978).…”

Section: Basic Hypothesesmentioning

confidence: 99%

“…1 (Dehlinger, 1978). The corrected values subtracts the reference gravity at the same point to yield gravity anomalies.…”

Section: Introductionmentioning

confidence: 99%

Three‐Dimensional Gravity Model Applied to Underwater Navigation

Yan¹,

Feng²,

Deng

et al. 2004

Acta Geologica Sinica (Eng)

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At present, new integrated navigation, which usesthe location function of reference gravity anomaly map to control the errors of the inertial navigation system (INS), has been developed in marine navigation. It is named the gravityaided INS. Both the INS and real-time computation of gravity anomalies need a 3-D marine normal gravity model. Conventionally, a reduction method applied in geophysical survey is directly introduced to observed data processing. This reduction does not separate anomaly from normal gravity in the observed data, so errors cannot be avoided. The 3-D marine normal gravity model was derived from the J2 gravity model, and is suitable for the region whose depth is less than lo00 m. Comparison of four gravity models. Papers to the Position Location and Navigation symposium, IEEE, 63 1-635. Hsu, D.Y., 1998. An accurate and efficient approximation to the normal gravity. Papers to the Position Location a d Navigation Symposium, IEEE, 38-44. Jircitano, A., and Dosch, D.E., 1991. Gravity aided inertid navigation system. Papers to the ION 47th Annual Meeting proceeding on Navigation and Explorarion, 22 1-229. Jircitano, A., White, J., and Doah, D., 1990. Gravity based navigation of AUVs, AW'90. Symposium on A W , 177-180. Mularie, W.M.. uw)o. Natwnal h w r y and Mapping Agtm,, Technical Report 8350.2 (third edition), 175. Rice. H., Mendehhn, L., Arons, R., and M -l a , D., 2000. Next generation marine precision navigation system. Papers to Position Location and Navigation Symposium, IEEE, 2W206. Shi Pan and Sun zhongmiao, 1999. "he solution to the problem of the spherical interior Dirichlet and its application. Acts Geodnetic et Cartographica Sinica, 28(3): 195-198 ( i n Chinese with English abstract). wei Ziqing, 2003. Normal gravity formulae. Actu Geodaetica et Cartographica Sinicu 32(2): 95-101 (in Chinese with English abstract),

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Marine gravity

Cited by 6 publications

References 17 publications

Improving the quality of marine geophysical track line data: Along‐track analysis

Improving the quality of marine geophysical track line data: Along‐track analysis

Errata‐based correction of marine geophysical trackline data

Three‐Dimensional Gravity Model Applied to Underwater Navigation

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