Evaluation of EGM2008 Within Geopotential Space from GPS, Tide Gauges and Altimetry
The new global Earth gravitational model EGM2008 has been evaluated within geopotential space by comparison with its predecessor EGM96 and the GRACE combination model EIGEN-GL04C. The methodology comprises establishing geodetic coordinates of mean sea level (MSL) from GPS observations, tide gauge (TG) time series and levelling. The gravity potential at MSL was estimated at each TG location by utilising the ellipsoidal harmonic coefficients of the adopted gravity field models to their maximum degree and order. This study uses data from 23 TGs around the Baltic Sea, nine in the UK and one in France. Comparison involves testing the agreement between geopotential values for each country as gravity potentials at MSL are supposed to be consistent for regions where mean dynamic topography (MDT) does not differ significantly. Results show significant improvement with the EGM2008 model compared against its counterparts. The study shows the effect of omission errors on the solution by limiting the EGM2008 model to maximum degree and order 360 in the regional study. In addition to the regional study, EGM2008 was also evaluated globally using MSL derived from altimetric data. The global study shows that W 0 , the potential value on the geoid, is not affected by high degree terms of the EGM2008.
KeywordsTide Gauge Omission Error Gravity Field Model Tropospheric Zenith Delay Mean Dynamic Topography
The authors would like to thank the following institutions for supplying data for this study: NASA JPL for GIPSY software and the provision of orbital products, NERC BIGF for GPS data at UK tide gauge sites and EUREF/IGS for Brest GPS data.
- Ardalan AA, Grafarend EW (2000) Reference ellipsoidal gravity potential field and gravity intensity field of degree/order 360/360 (manual of using ellipsoidal harmonic coefficients ellipfree.dat and ellipmean.dat). http://www.uni-stuttgart.de/gi/research/index.html#projects
- Blewitt G (2008) Fixed point theorems of GPS carrier phase ambiguity resolution and their application to massive network processing: Ambizap. J Geophys Res B Solid Earth 113(12)Google Scholar
- Boehm J, Werl B, Schuh H (2006) Troposphere mapping functions for GPS and very long baseline interferometry from European Centre for Medium-Range Weather Forecasts operational analysis data. J Geophys Res B Solid Earth 111(2)Google Scholar
- Förste C, Flechtner F, Schmidt R, König R, Meyer U, Stubenvoll R, Rothacher M, Barthelmes F, Neumayer H, Biancale R (2006) A mean global gravity field model from the combination of satellite mission and altimetry/gravimetry surface data: EIGEN-GL04C. Geophys Res Abstr 8:03462Google Scholar
- Hernandez F, Schaeffer P (2001) The CLS01 mean sea surface: a validation with the GSFC00 surface. press, CLS Ramonville StAgne, FranceGoogle Scholar
- Lemoine FG, Kenyon SC, Factor JK, Trimmer RG, Pavlis NK, Chinn DS, Cox CM, Klosko SM, Luthcke SB, Torrence MH (1998) The Development of the Joint NASA GSFC and the National Imagery and Mapping Agency(NIMA) Geopotential Model EGM 96. NASA, (19980218814)Google Scholar
- McCarthy DD, Petit G (2004) IERS Conventions 2003. IERS Technical Note, 32, p 127Google Scholar
- Pavlis N, Kenyon S, Factor J, Holmes S (2008) Earth gravitational model 2008. In SEG Technical Program Expanded Abstracts, vol 27:761–763Google Scholar
- Poutanen M, Kakkuri J (1999) Final results of the Baltic Sea level 1997 GPS Campaign. Rep Finnish Geodetic Institute. 99(2)Google Scholar
- Roemmich D, Riser S, Davis R, Desaubies Y (2004) Autonomous profiling floats: workhorse for broadscale ocean observations. J Mar Technol Soc 38:31–39Google Scholar
- Sanchez L (2008) Approach for the establishment of a global vertical reference level. In: Proceedings of the VI Hotine-Marussi Symposium, Springer, May 2008Google Scholar