Journal of Geodesy

, Volume 81, Issue 5, pp 359–368 | Cite as

A comparison of GPS, VLBI and model estimates of ocean tide loading displacements

  • Ian D. ThomasEmail author
  • Matt A. King
  • Peter J. Clarke
Original Article


In recent years, ocean tide loading displacements (OTLD) have been measured using the Global Positioning System (GPS) and Very Long Baseline Interferometry (VLBI). This study assesses the accuracy of GPS measurements of OTLD by comparison with VLBI measurements and estimates derived from numerical ocean tide models. A daily precise point positioning (PPP) analysis was carried out on ∼11 years of GPS data for each of 25 sites that have previous OTLD estimates based on data from co-located VLBI sites. Ambiguities were fixed to integer values where possible. The resulting daily estimates of OTLD, at eight principal diurnal and semi-diurnal tidal frequencies, were combined to give GPS measurements of OTLD at each site. The 3D GPS and VLBI measurements of OTLD were compared with estimates computed (by convolution with Green’s functions) from five modern ocean tide models (CSR4.0, FES2004, GOT00.2, NAO99b and TPXO6.2). The GPS/model agreement is shown to be similar to the VLBI/model agreement. In the important radial direction, the GPS/model misfit is shown to be smaller than the VLBI/model misfit for seven of the eight tidal constituents; the exception being the K2 constituent. Fixing of GPS carrier-phase ambiguities to integer values resulted in a marginal improvement to the GPS/model agreement. Statistically, it is shown there is no significance to the difference between the fit of the GPS and VLBI measurements of OTLD to modelled values. Equally, differences in fit of either the complete set of GPS or VLBI estimates to the five sets of model-derived values cannot be identified with statistical significance. It is thus concluded that, overall, we cannot distinguish between GPS and VLBI measurements of OTLD, and that at the global scale, present ocean tide models are accurate to within the current measurement noise of these techniques.


GPS Ocean tide loading (OTL) Ocean tide loading displacement (OTLD) VLBI Ocean tide models 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Allinson CR, Clarke PJ, Edwards SJ, King MA, Baker TF, Cruddace PR (2004) Stability of direct GPS estimates of ocean tide loading. Geophys Res Lett 31(15). Doi 10.1029/2004GL020588Google Scholar
  2. Baker TF, Bos MS (2003) Validating Earth and ocean tide models using tidal gravity measurements. Geophys J Int 152(2): 468–485CrossRefGoogle Scholar
  3. Beutler G, Rothacher M, Schaer S, Springer TA, Kouba J, Neilan RE (1999) The International GPS Service (IGS): an interdisciplinary service in support of Earth sciences. Adv Space Res 23(4):631–635CrossRefGoogle Scholar
  4. Crossley D (2004) Preface to the Global Geodynamics Project. J Geodyn 38(3–5):225–236CrossRefGoogle Scholar
  5. Eanes RJ, Bettadpur SV (1995) The CSR 3.0 global ocean tide model. Technical Memorandum CSR-TM-96-05, Center for Space Research, University of Texas at AustinGoogle Scholar
  6. Egbert GD, Erofeeva L (2002) Efficient inverse modeling of barotropic ocean tides. J Atmos Ocean Technol 19.Google Scholar
  7. Farrell WE (1972) Deformation of Earth by surface loads. Rev Geophys Space Phys 10(3):761–797Google Scholar
  8. Field A (2003) Discovering statistics: using SPSS for Windows. Sage,Google Scholar
  9. Godin G (1972) The analysis of tides. Liverpool University Press, LiverpoolGoogle Scholar
  10. King M (2005) Kinematic and static GPS techniques for estimating tidal displacements with application to Antarctica. J Geodyn. DOI 10.1016/j.jog.2005.08.019Google Scholar
  11. King M, Coleman R, Nguyen LN (2003) Spurious periodic horizontal signals in sub-daily GPS position estimates. J Geod 77(1–2):15–21CrossRefGoogle Scholar
  12. King MA, Penna NT, Clarke PJ, King EC (2005) Validation of ocean tide models around Antarctica using onshore GPS and gravity data. J Geophys Res 110(B8):B08401. DOI 10.1029/2004JB003390Google Scholar
  13. Lefevre F, Yard FH, Le Provost C, Schrama EJO (2002) FES99: A global tide finite element solution assimilating tide gauge and altimetric information. J Atmos Ocean Technol 19(9): 1345–1356CrossRefGoogle Scholar
  14. Llubes M, Mazzega P (1997) The ocean tide gravimetric loading reconsidered. Geophys Res Lett 23(12):1481–1484CrossRefGoogle Scholar
  15. Matsumoto K, Takanezawa T, Ooe M (2000) Ocean tide models developed by assimilating TOPEX/Poseidon altimeter data into hydrodynamical model: a global model and a regional model around Japan. J Oceanogr 56:567–581CrossRefGoogle Scholar
  16. McCarthy DD, Petit G (eds) (2004) IERS Technical Note 32. IERS Conventions (2003), International Earth Rotation and Reference Systems Service (IERS). Verlag des Bundesamtes für Kartographie und Geodäsie, Frankfurt am MainGoogle Scholar
  17. McCarthy DD (ed.) (1996) IERS Technical Note 21. IERS Conventions (1996), International Earth Rotation and Reference Systems Service (IERS). Verlag des Bundesamtes für Kartographie und Geodäsie, Frankfurt am MainGoogle Scholar
  18. Petrov L, Ma CP (2003) Study of harmonic site position variations determined by very long baseline interferometry. J Geophys Res 108(B4):2190CrossRefGoogle Scholar
  19. Ray RD, Ponte RM (2003) Barometric tides from ECMWF operational analyses. Ann Geophys 21(8):1897–1910CrossRefGoogle Scholar
  20. Schenewerk MS, Marshall J, Dillinger W (2001) Vertical ocean-loading deformations derived from a global GPS network. J Geod Soc Jpn 47(1):237–242Google Scholar
  21. Scherneck H-G (1999) Explanatory supplement to the section “Local site displacement due to ocean loading” of the IERS Conventions. Explanatory supplement to the IERS Conventions (1996) Chaps. 6 and 7. IERS Technical Note 21, International Earth Rotation and Reference Systems Service (IERS). Verlag des Bundesamtes für Kartographie und Geodäsie, Frankfurt am MainGoogle Scholar
  22. Sovers OJ (1994) Vertical ocean loading amplitudes from VLBI measurements. Geophys Res Lett 21(5):357–360CrossRefGoogle Scholar
  23. Tamura Y (1987) A harmonic development of the tide-generating potential. Bull Inf Mar Terr 99:6813–6857Google Scholar
  24. Webb FH, Zumberge JF (1995) An introduction to GIPSY/OASIS-II precision software for the analysis of data from the Global Positioning System. Report D-11088, Jet Propulsion Laboratory, PasadenaGoogle Scholar
  25. Zumberge JF, Heflin MB, Jefferson DC, Watkins MM, Webb FH (1997) Precise point positioning for the efficient and robust analysis of GPS data from large networks. J Geophys Res 102(B3):5005–5017CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • Ian D. Thomas
    • 1
    Email author
  • Matt A. King
    • 1
  • Peter J. Clarke
    • 1
  1. 1.School of Civil Engineering and GeosciencesNewcastle UniversityNewcastle upon TyneUK

Personalised recommendations