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| Titel |
Innovative Remote Sensing: Flood Monitoring using GNSS Reflectometry |
| VerfasserIn |
Jamila Beckheinrich, Angelika Hirrle, Steffen Schön, Georg Beyerle, Maximillian Semmling, Heiko Apel, Jens Wickert |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094536
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| Publikation (Nr.) |
 EGU/EGU2014-9949.pdf |
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| Zusammenfassung |
| An increase of the intensity and frequency of extreme precipitation events are observed in the
last decade due to climate changing conditions. Resulting floods pose significant
socio-economic problems in areas like on the banks of the Mekong Delta with dense
population. To quantify and predict the impact of these flooding events to the local population
it is important to measure and understand the related hydrological processes. Satellite based
altimetry offers water level measurements with high accuracy for oceans and very large rivers
but typically with insufficient spatio-temporal resolution. The accuracy decreases in coastal
areas. Water level gauging instruments offer a high accuracy and temporal resolution but
for a single location only. However, the number of water level gauging stations
worldwide is decreasing. GNSS-Reflectometry (GNSS-R) can fill the gap between
these two measurement methods. Earth reflected L-band signals from the Global
Navigation Satellite Systems (GNSS) show a high reflectivity on water surfaces. This
property is used to derive water level height changes. In principle two different
GNSS-R altimetry methods exist: based on code or carrier phase observations. Our
research activities focus on the phase-based altimetric application of GNSS-R. In
March 2012, a two-week measurement campaign was conducted in Can Tho City,
Vietnam within the WISDOM (Water related Information System for the sustainable
Development Of the Mekong Delta) research project. Several reflection traces on the
150 m wide Can Tho River section are recorded with a dedicated GNSS-R receiver
developed in cooperation between GFZ and JAVAD. To track the direct and the reflected
signal separately, two antennas are used. The analysis of the recorded signals shows
a superposition of the signal reflected by the water surface with other multipath
signals. These occur due to the surrounding of the antennas (vegetation, buildings).
To separate these different multipath signals and to filter out the one reflected by
the water surface an adapted Hilbert Huang Transform (HHT) and a model of the
observations are applied. The HHT offers the advantage that no a priori base is needed
like the trigonometric functions in case of Fourier Transform or a mother wavelet
in case of Wavelet Transform. No stationarity or linearity of the signal has to be
assumed, as it is a fully data-driven signal analysis method. In a second step, a
Least-Squares Method is used to determine the water level height. First results
show a correlation of 0.84 (RMS 5 cm) with water level changes registered from a
water level gauging instrument placed 8 km away from the measurement place. |
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