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GNSS Amplitude Estimation - A concept to measure Soil Moisture and Sea-Ice Concentration

Maximilian Semmling
Laboratoire d’Informatique, Signal et Image de la Côte d’Opale (LISIC)
Deutsches GeoForschungsZentrum (GFZ), Potsdam, Germany

jeudi 25 octobre 2018 à 13h30


Signals of Global Navigation Satellite Systems (GNSS) give the opportunity to investigate new concepts for Earth observation studying, e.g., a bi-static reflectometry system. Parameters of the Earth reflected GNSS signal, like the carrier phase and amplitude, can be used for soil moisture estimation, sea ice detection or sea surface altimetry. A coherent tracking of the signal, using in-phase and quadrature components, is beneficial to increase the precision of the retrieved parameters. Experiments on coherent reflection tracking have been conducted successfully on ground, airborne and from space. A potential assimilation of coherent reflectometry results revealed a benefit for Earth observation. Current challenges arise for the amplitude estimation concept and a reliable signal tracking for moving receiver platforms. The here presented concept focuses on the link of amplitude estimates and its sensitivity to near-surface permittivity that allows to invert parameters like soil moisture and sea ice concentration.
Two experiments and the corresponding inversion results are presented, first, on soil moisture and, second, on sea ice concentration. A first experiment was conducted within the MARCO project (Marine Research at Côte d’Opale). It involves a ground-based reflectometry setup used for measurements over sand-dominated soil at les Hemmes, Pas-de-Calais, France. Four stations with different soil moisture conditions have been realized there and were combined with in-situ measurements characterizing structure and moisture of the soil. The second experiment was conducted with a ship-based reflectometry setup on the Norwegian research vesssel Lance. It gathered a data set over 20 days navigating through waters with sea ice in Fram Strait, Arctic Ocean. Different sea ice scenarios from ice-free (0% concentration) up to complete coverage (100% concentration) are investigated. The measurements also comprised ancillary data to validate the sea ice concentration and to determine the corresponding ice type. The concept of amplitude estimation, linked to the near-surface permittivity, is applied in a similar way for both experiments. It allows to estimate the state of soil moisture or sea ice concentration, respectively. A future challenge is to apply the concept at higher estimation rates for receivers on an unmanned aerial vehicle (uav) or a satellite.

Joined work with : G. Stienne (1), J-C. Kucwaj (1), S. Gontharet (3), S. Gerland (4), S. Reboul (1), J. Wickert (2)
(1) Laboratoire d’Informatique, Signal et Image de la Côte d’Opale (LISIC, EA 4491), Calais, France
(2) Deutsches GeoForschungsZentrum (GFZ), Potsdam, Germany
(3) Laboratoire d’Océanologie et de Géosciences (LOG, UMR 8187 CNRS ULCO UL), Wimereux, France
(4) Norsk Polarinstitutt (NPI), Tromsø, Norway