Journal of Geodesy

, Volume 89, Issue 3, pp 241–258 | Cite as

Levelling co-located GNSS and tide gauge stations using GNSS reflectometry

  • Alvaro Santamaría-GómezEmail author
  • Christopher Watson
  • Médéric Gravelle
  • Matt King
  • Guy Wöppelmann
Original Article


The GNSS reflectometry technique provides geometric information on the environment surrounding the GNSS antenna including the vertical distance to a reflecting surface. We use sea-surface reflections of GPS signals, recorded as oscillations in signal-to-noise ratio (SNR), to estimate the GNSS to tide gauge (TG) levelling tie, and thus the ellipsoidal heights of the TG. We develop approaches to isolate SNR data dominated by sea-surface reflections and to remove SNR frequency changes caused by the dynamic sea surface. Comparison with in situ levelling at eight sites reveals mean differences at the centimetre level for satellites above 12\(^{\circ }\) elevation, with four sites showing differences of 3 cm or smaller. These differences include errors in the in situ levelling, in the antenna calibration model and in the TG measurements, and so represent an upper bound on our technique’s error. Data sampling (1 or 30 s) does not significantly affect the results. We detect systematic errors at the decimetre level related to satellite elevations below 12\(^{\circ }\) and to sea-surface height and also differences between results from the L1 and L2 GPS signals larger than 15 cm at two sites. These systematic errors remain unexplained; differences between GPS signals are attributed to receiver-dependent differences in the SNR measurements, while the elevation-dependent error is attributed to unmodelled phase effects such as those caused by tropospheric refraction and sea-surface roughness. Using our approach, we identify a levelling offset of 1.5 cm related to a TG sensor change, illustrating our technique’s value for TG reference monitoring.


Reflectometry GNSS SNR Levelling  Tide gauges Site co-location 



A. SG. is a recipient of a FP7 Marie Curie International Outgoing Fellowship (Project Number 330103). M. A. K. is a recipient of an Australian Research Council Future Fellowship (Project Number FT110100207). We acknowledge Kristine M. Larson, Felipe G. Nievinski, the editor and an anonymous reviewer for constructive comments. We acknowledge the Système d’Observation du Niveau des Eaux Littorales (SONEL), Institut National de l’Information Géographique et Forestière (IGN), Geoscience Australia (GA), and Instituto Geográfico Nacional (IGN) for providing the GPS data, and the Service Hydrographique et Oceanographique de la Marine (SHOM), Australian Bureau of Meteorology (BOM), and Puertos del Estado (REDMAR network) for providing the tide gauge data. Google Earth provided the satellite images. Figures 5, 6, 7 and 8 were produced with Gnuplot.

Supplementary material

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Supplementary material 1 (docx 14 KB)
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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Alvaro Santamaría-Gómez
    • 1
    • 2
    Email author
  • Christopher Watson
    • 2
  • Médéric Gravelle
    • 1
  • Matt King
    • 2
  • Guy Wöppelmann
    • 1
  1. 1.LIENSs, University of La Rochelle - CNRSLa RochelleFrance
  2. 2.School of Land and FoodUniversity of TasmaniaHobartAustralia

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