EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Airborne GNSS reflectometry for coastal monitoring of sea state

Mario Moreno1,2, Maximilian Semmling2,3, Georges Stienne4, Serge Reboul4, and Jens Wickert1,2
Mario Moreno et al.
  • 1Technische Universität Berlin (TUB), Germany. (
  • 2Deutsches GeoForschungsZentrum Potsdam (GFZ), Potsdam, Germany.
  • 3Institute for Solar-terrestrial Physics (DLR-SO), Neustrelitz, Germany.
  • 4Laboratoire d’Informatique, Signal et Image de la Côte d’Opale (LISIC), Université du Littoral Côte d'Opale (ULCO), Calais, France.

Global Satellite Navigation Systems (GNSS) applications like navigation and positioning generally focus on the use of the direct radio signal broadcasted by the navigation satellites. From these signals, very highly precise coordinates can be obtained. However, there is a proportion of signals, that do not reach the receivers directly, that is, the signals that are reflected off Earth’s surface before reaching the receivers. That phenomenon gave way to one of the techniques that is taking an important role in the scope of GNSS remote sensing called GNSS-Reflectometry (GNSS-R). Due to the high reflection coefficient of the water and its importance within the climate system, the ocean is one of the surfaces with greatest interest in GNSS-R research projects. The objective of this study is to retrieve information about ocean height measured through the delay of the signal, and sea state and wind retrieval (ocean surface roughness) from the analysis of the signal amplitude.

During this study, GNSS-R measurements were executed along the North Sea coast between the cities of Calais and Boulogne, France, onboard of a gyrocopter. The setup consisted of a front-end data recorder with a right-handed circular polarization (RHCP) antenna. The campaign was conducted in July 2019 within a total of 9h 40m flight time. Each flight was performed at an altitude of about 800 m above sea level going on two legs forth and back along the coast. The legs differed in the distance from the coastline, of 700 m and 2 km, respectively.

Reflectometry signal processing involves three data levels. Level (0): The raw data samples of Syntony front-end receiver. Level (1): The Delay-Doppler Map (DDM) of the correlated reflected signal and the carrier phase, from which geophysical information can be derived. And Level (2): height estimation (from signal correlation in delay and frequency domain) and roughness estimation (from signal amplitude).

By using the DDM and the carrier phase delay the sea state shall be assessed including the achievable precision and reliability of estimates. An additional aim is also to validate the configuration in terms of the used platform, antenna setup, and flight design.

How to cite: Moreno, M., Semmling, M., Stienne, G., Reboul, S., and Wickert, J.: Airborne GNSS reflectometry for coastal monitoring of sea state, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19944,, 2020


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