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

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## Abstract

A terrestrial survey, called the Geoid Slope Validation Survey of 2011 (GSVS11), encompassing leveling, GPS, astrogeodetic deflections of the vertical (DOV) and surface gravity was performed in the United States. The general purpose of that survey was to evaluate the current accuracy of gravimetric geoid models, and also to determine the impact of introducing new airborne gravity data from the ‘Gravity for the Redefinition of the American Vertical Datum’ (GRAV-D) project. More specifically, the GSVS11 survey was performed to determine whether or not the GRAV-D airborne gravimetry, flown at 11 km altitude, can reduce differential geoid error to below 1 cm in a low, flat gravimetrically uncomplicated region. GSVS11 comprises a 325 km traverse from Austin to Rockport in Southern Texas, and includes 218 GPS stations (\(\sigma _{\Delta h }= 0.4\) cm over any distance from 0.4 to 325 km) co-located with first-order spirit leveled orthometric heights (\(\sigma _{\Delta H }= 1.3\) cm end-to-end), including new surface gravimetry, and 216 astronomically determined vertical deflections \((\sigma _{\mathrm{DOV}}= 0.1^{\prime \prime })\). The terrestrial survey data were compared in various ways to specific geoid models, including analysis of RMS residuals between all pairs of points on the line, direct comparison of DOVs to geoid slopes, and a harmonic analysis of the differences between the terrestrial data and various geoid models. These comparisons of the terrestrial survey data with specific geoid models showed conclusively that, in this type of region (low, flat) the geoid models computed using existing terrestrial gravity, combined with digital elevation models (DEMs) and GRACE and GOCE data, differential geoid accuracy of 1 to 3 cm (1 \(\sigma )\) over distances from 0.4 to 325 km were currently being achieved. However, the addition of a contemporaneous airborne gravity data set, flown at 11 km altitude, brought the estimated differential geoid accuracy down to 1 cm over nearly all distances from 0.4 to 325 km.

## Keywords

Geoid GRAV-D GSVS11 NAVD 88 Geoid accuracy Airborne gravity Geodetic surveying Gravimetry Deflections of the vertical Astro-geodesy## Notes

### Acknowledgments

Above all others, the authors wish to thank the 96 separate individuals from within the National Geodetic Survey who participated to some extent in this survey, including 46 who actually performed the field work. The authors also wish to thank the Texas governor’s office, the Texas State Troopers, the Texas Department of Transportation, the Texas Maritime Museum, the Texas General Lands Office, the Texas Natural Resources Information System, the University of Texas, Bowie High School and all other representatives of the Lone Star State for welcoming us, and allowing us to work safely and unhindered on the grounds of the capital building, along the highways of Texas as well inside the Stephen F. Austin Building, the Texas Maritime Museum, Pickle Research Campus and Bowie High School.

## References

- Bürki, B, Müller A, Kahle H-G (2004) DIADEM: the new digital astronomical deflection measuring system for high-precision measurements of deflections of the vertical at ETH Zurich. IAG GGSM2004 Meeting in Porto, PortugalGoogle Scholar
- Childers VA (1996) Gravimetry as a geophysical tool: airborne gravimetry and studies of lithospheric flexure and faulting. PhD dissertation, Columbia UniversityGoogle Scholar
- Childers VA, Bell RE, Brozena JM (1999) Airborne gravimetry: an investigation of filtering. Geophysics 64(1):61–69CrossRefGoogle Scholar
- Diehl TM, Holt JW, Blankenship DD, Young DA, Jordan TA, Ferraccioli F (2008) First airborne gravity results over the thwaites glacier catchment, West Antarctica. Geochem Geophys Geosyst 9(1)Google Scholar
- Farr TG, Rosen P, Caro E, Crippen R, Duren R, Hensley S, Kobrick M, Paller M, Rodriguez E, Roth L, Seal D, Shaffer S, Shimada J, Umland J, Werner M, Oskin M, Burbank D, Alsdorf D (2007) The shuttle radar topography mission. Rev Geophys 45(2)Google Scholar
- Featherstone W, Lichti D (2009) Fitting gravimetric geoid models to vertical deflections. J Geod 83:583–589CrossRefGoogle Scholar
- Federal Geodetic Control Committee (1984) Standards and Specifications for Geodetic Control NetworksGoogle Scholar
- Flury J, Rummel R (2009) On the geoid-quasigeoid separation in mountain areas. J Geod 83:829–847CrossRefGoogle Scholar
- Forsberg R (1984) A study of terrain reductions, density anomalies and geophysical inversion methods in gravity field modelling. Reports of the Department of Geodetic Science and Surveying, #355. The Ohio State University, Columbus, OhioGoogle Scholar
- Forsberg R, Ses S, Alshamsi A, Hassan A (2012) Coastal geoid improvement using airborne gravimetric data in the United Arab Emirates. Int J Phys Sci 7(45):6012–6023Google Scholar
- Goiginger H (2011) The combined satellite-only global gravity field model GOCO02S. In: European Geosciences Union General Assembly 2011Google Scholar
- GRAV-D Science Team (2011) Gravity for the redefinition of the American Vertical Datum (GRAV-D) Project, Airborne Gravity Data; Block CS04. http://www.ngs.noaa.gov/GRAV-D/data_cs04.shtml. Accessed 05 Oct 2011
- Gruber T, Visser P, Ackermann C, Hosse M (2011) Validation of GOCE gravity field models by means of orbit residuals and geoid comparisons. J Geod 85:845–860CrossRefGoogle Scholar
- Heiskanen WA, Moritz H (1967) Physical geodesy. W.H. Freeman and Co., San FranciscoGoogle Scholar
- Hirt C, Gruber T, Featherstone W (2011) Evaluation of the first GOCE static gravity field models using terrestrial gravity, vertical deflections and EGM2008 quasigeoid heights. J Geod 85:723–740CrossRefGoogle Scholar
- Hirt C (2006) Monitoring and analysis of anomalous refraction using a digital zenith camera system. A &A 459(1):283–290Google Scholar
- Hirt C, Bürki B, Somieski A, Seeber G (2010) Modern determination of vertical deflections using digital zenith cameras. J Surv Eng 136(1):1–12 Google Scholar
- Holmes SA, Pavlis N (2007) Some aspects of harmonic analysis of data gridded on the ellipsoid. In: Gravity field of the Earth, Proceedings of the 1st International Symposium of the International Gravity Field Service (IGFS), IstanbulGoogle Scholar
- Hsiao Y, Hwang C (2010) Topography-assisted downward continuation of airborne gravity: an application for geoid determination in Taiwan. Terr Atmos Ocean Sci 21(4):627–637CrossRefGoogle Scholar
- Jekeli C (1988) The exact transformation between ellipsoidal and spherical harmonic expansions. Manuscripta Geodaetica 13(2):106–113Google Scholar
- Kotsakis C, Sideris M (1999) On the adjustment of combined GPS/leveling/geoid networks. J Geod 73:412–421CrossRefGoogle Scholar
- Kurtenbach E, Mayer-Gürr T, Eicker A (2009) Deriving daily snapshots of the Earth’s gravity field from GRACE L1B data using Kalman filtering. Geophys Res Lett 36(17)Google Scholar
- Mader G, Schenewerk M, Weston N, Evjen J, Tadepalli K, Neti J (2012) Interactive web-based GPS network processing and adjustment using NGS’ OPUS-projects. In: Proceedings of the FIG working week 2012, Rome, ItalyGoogle Scholar
- Mayer-Gürr T (2007) ITG-GRACE03S: the latest GRACE gravity field solution computed in Bonn. In: Presentation at GSTM+SPP, 15–17 October 2007Google Scholar
- Milbert D (1995) Improvement of a high resolution geoid model in the United States by GPS height on NAVD88 benchmarks. Bull Int Geoid Serv 4:13–36Google Scholar
- Moritz H (1980) Advanced Physical Geodesy. Herbert Wichmann, KarlsruheGoogle Scholar
- Pavlis NK (1998) The block-diagonal least-squares approach. In: The development of the joint NASA GSFC and the National Imagery and Mapping Agency (NIMA) Geopotential Model EGM96, by NASA. NASA Goddard Space Flight Center, Washington, DC, pp 8.4–8.5.Google Scholar
- Pavlis NK, Holmes SA, Kenyon S, Factor JK (2012) The development and evaluation of the Earth Gravitational Model 2008 (EGM2008). J Geophys Res 117(B4)Google Scholar
- Rapp R (1997) Use of potential coefficient models for geoid undulation determinations using a spherical harmonic representation of the height anomaly/geoid undulation difference. J Geod 71:282–289CrossRefGoogle Scholar
- Smith DA (2011) True Zero. Point Begin 37(3):20–25Google Scholar
- Smith DA, Milbert DG (1999) The GEOID96 high-resolution geoid height model for the United States. J Geod 73:219–236CrossRefGoogle Scholar
- Smith DA (1998) There is no such thing as “the” EGM96 geoid: Subtle points on the use of a global geopotential model. Bull Int Geoid Serv 8:17–28Google Scholar
- Torge W (2001) Geodesy. W. de Gruyter, BerlinGoogle Scholar
- Voigt C, Denker H, Hirt C (2008) Regional astrogeodetic validation of GPS/leveling data and quasigeoid models. In: Observing our changing earth. Springer, Berlin, pp 413–420Google Scholar
- Wang YM, Saleh J, Roman DR (2012) The US Gravimetric Geoid of 2009 (USGG2009): model development and evaluation. J Geod 86:165–180CrossRefGoogle Scholar
- Weston N, Soler T, Mader G (2007) Web-based Solution for GPS Data: NOAA OPUS. GIM International, April 2007, pp 23–25Google Scholar
- Wong L, Gore R (1969) Accuracy of geoid heights from modified stokes kernals. Geophys J R Astronom Soc 19:81–91CrossRefGoogle Scholar
- Zilkoski DB, Richards JH, Young GM (1992) Results of the general adjustment of the North American Vertical Datum of 1998. Surv Land Inf Syst 52(3):133–149Google Scholar