Confirming regional 1 cm differential geoid accuracy from airborne gravimetry: the Geoid Slope Validation Survey of 2011

Smith, D. A.; Holmes, S. A.; Li, Xiaopeng; Guillaume, Sébastien; Wang, Yan Ming; Bürki, Beat; Roman, D. R.; Damiani, T.

doi:10.1007/s00190-013-0653-0

Cited by 58 publications

(43 citation statements)

References 20 publications

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“…However, the uncertainty of geometric levelling depends on many factors, with some of the levelling errors behaving in a random manner and propagating with the square root of the number of individual set-ups or the distance, respectively, while other errors of systematic type may propagate with distance in a less favourable way. Consequently, it is important to keep in mind that geometric levelling is a differential technique and hence may be susceptible to systematic errors; examples include the differences between the second and third geodetic levelling in Great Britain (about 0.2 m in the northsouth direction over about 1000 km distance; Kelsey 1972), corresponding differences between an old and new levelling in France (about 0.25 m from the Mediterranean Sea to the North Sea, also mainly in north-south direction, distance about 900 km; Rebischung et al 2008), and inconsistencies of more than ±1 m across Canada and the USA (differences between different levellings and with respect to an accurate geoid; Véronneau et al 2006;Smith et al 2010Smith et al , 2013. In addition, a further complication with geometric levelling in different countries is that the results are usually based on different tide gauges with offsets between the corresponding zero level surfaces, which, for example, reach more than 0.5 m across Europe.…”

Section: Uncertainty Considerationsmentioning

confidence: 99%

Geodetic methods to determine the relativistic redshift at the level of 10 $$^{-18}$$ - 18 in the context of international timescales: a review and practical results

Denker

Timmen

Voigt

et al. 2017

J Geod

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The frequency stability and uncertainty of the latest generation of optical atomic clocks is now approaching the one part in 10 18 level. Comparisons between earthbound clocks at rest must account for the relativistic redshift of the clock frequencies, which is proportional to the corresponding gravity (gravitational plus centrifugal) potential difference. For contributions to international timescales, the relativistic redshift correction must be computed with respect to a conventional zero potential value in order to be consistent with the definition of Terrestrial Time. To benefit fully from the uncertainty of the optical clocks, the gravity potential must be determined with an accuracy of about 0.1 m 2 s −2 , equivalent to about 0.01 m in height. This contribution focuses on the static part of the gravity field, assuming that temporal variations are accounted for separately by appropriate reductions. Two geodetic approaches are investigated for the derivation of gravity potential values: geometric levelling and the Global Navigation Satellite Systems (GNSS)/geoid approach. Geometric levelling gives potential differences with millimetre uncertainty over shorter distances (several kilometres), but is susceptible to systematic errors at the decimetre level over large distances. The GNSS/geoid approach gives absolute gravity potential values, but with an uncertainty corresponding to about 2 cm in height. For large distances, the GNSS/geoid approach should therefore be better than geometric levelling. This is demonstrated by the results from practical investigations related to three clock sites in Germany and one in France. The estimated uncertainty for the relativistic redshift correction at each site is about 2 × 10 −18 .

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Section: Uncertainty Considerationsmentioning

confidence: 99%

Geodetic methods to determine the relativistic redshift at the level of 10 $$^{-18}$$ - 18 in the context of international timescales: a review and practical results

Denker

Timmen

Voigt

et al. 2017

J Geod

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“…These results demonstrate that the GRAV‐D data improves the accuracy of GGMs, and their associated geoid models, in the test areas. Although the GRAV‐D data in other regions have been independently verified as improving the geoid [ Smith et al ., ; Wang et al ., ], this is the first time that such a significant improvement by airborne gravity in such an extensive area in the U.S. has been demonstrated. This is encouraging as NGS prepares to transition to a geoid‐based vertical datum in 2022.…”

Section: Resultsmentioning

confidence: 99%

“…Smith et al . [] and Wang et al . [] performed case studies in Texas and Iowa and demonstrated that such accuracies could be achieved with the GRAV‐D data.…”

Section: Introductionmentioning

confidence: 99%

“…This airborne gravimetry will augment and correct existing terrestrial gravity data, to be ultimately combined with satellite gravity models [e.g., Tapley et al, 2004;Rummel et al, 2011] and other data (e.g., digital elevation models, satellite altimetry) to yield the targeted geoid accuracy: ±1-2 cm in flat areas and ±2-3 cm in higher elevations. Smith et al [2013] and Wang et al [2015] performed case studies in Texas and Iowa and demonstrated that such accuracies could be achieved with the GRAV-D data.…”

Section: Introductionmentioning

confidence: 99%

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The contribution of the GRAV‐D airborne gravity to geoid determination in the Great Lakes region

Crowley

Holmes

et al. 2016

Geophysical Research Letters

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The current official North American Vertical Datum of 1988 (NAVD 88) and the International Great Lakes Datum of 1985 (IGLD 85) will be replaced by a new geoid‐based vertical datum in 2022. The Gravity for the Redefinition of the American Vertical Datum (GRAV‐D) project collects high‐quality airborne gravity data to improve the quality of the gravitational model that underpins the geoid model. This paper validates the contribution of GRAV‐D data in the Great Lakes region. Using the lake surface height measured by satellite altimetry as an independent data set, Global Gravity Models (GGMs) with/without the GRAV‐D data are compared. The comparisons show that the improvement reaches decimeters over Lake Michigan where the historic gravity data have significant errors. Over all lakes, except Lake Erie, the GRAV‐D data improve the accuracy of the gravitational model to 1–3 cm.

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“…Hence, the gravimetric geoid models that contain these satellite models should have equivalent accuracy in the long wavelength. Furthermore, recent studies have shown that the airborneenhanced NGS xGeoid models have about a 1-2 cm accuracy at the newly observed independent leveling lines (Smith et al 2013) and at the multi-year averaged mean altimetry passes over the Great Lakes (Li et al 2016). However, when compared with the GPS/Leveling determined geoid values at the NAVD 88 benchmarks, all of the above mentioned geoid models show signi cant di erences to this leveling based vertical datum.…”

Section: Statement Of the Problemmentioning

confidence: 91%

Modeling the North American vertical datum of 1988 errors in the conterminous United States

Li¹

2018

Journal of Geodetic Science

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A large systematic di erence (ranging from − cm to + cm) was found between NAVD 88 (North American Vertical Datum of 1988) and the pure gravimetric geoid models. This di erence not only makes it very dicult to augment the local geoid model by directly using the vast NAVD 88 network with state-of-the-art technologies recently developed in geodesy, but also limits the ability of researchers to e ectively demonstrate the geoid model improvements on the NAVD 88 network. Here, both conventional regression analyses based on various prede ned basis functions such as polynomials, B-splines, and Legendre functions and the Latent Variable Analysis (LVA) such as the Factor Analysis (FA) are used to analyze the systematic di erence. Besides giving a mathematical model, the regression results do not reveal a great deal about the physical reasons that caused the large di erences in NAVD 88, which may be of interest to various researchers. Furthermore, there is still a signi cant amount of no-Gaussian signals left in the residuals of the conventional regression models. On the other side, the FA method not only provides a better t of the data, but also o ers possible explanations of the error sources. Without requiring extra hypothesis tests on the model coe cients, the results from FA are more e cient in terms of capturing the systematic di erence. Furthermore, without using a covariance model, a novel interpolating method based on the relationship between the loading matrix and the factor scores is developed for predictive purposes. The prediction error analysis shows that about 3-7 cm precision is expected in NAVD 88 after removing the systematic di erence.

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Confirming regional 1 cm differential geoid accuracy from airborne gravimetry: the Geoid Slope Validation Survey of 2011

Cited by 58 publications

References 20 publications

Geodetic methods to determine the relativistic redshift at the level of 10 $$^{-18}$$ - 18 in the context of international timescales: a review and practical results

Geodetic methods to determine the relativistic redshift at the level of 10 $$^{-18}$$ - 18 in the context of international timescales: a review and practical results

The contribution of the GRAV‐D airborne gravity to geoid determination in the Great Lakes region

Modeling the North American vertical datum of 1988 errors in the conterminous United States

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