GNSS-R, an Innovative Remote Sensing Tool for the Mekong Delta, Jamila Beckheinrich, Brest 2013Slide 1

GNSS Reflectometry, an Innovative Remote Sensing Tool for the Mekong Delta

J. Beckheinrich1, S. Schön2, G. Beyerle1, M. Semmling1, H. Apel1, J. Wickert1

1.GFZ, German Research Center for Geosciences, Potsdam, Germany2.Leibniz University Hannover, Institute of Geodesy, Hannover, Germany

Space Reflecto 2013Brest, France

WP within the WISDOM project

Experimental Setup

Data Analysis

Latest Results

Conclusion and Outlook

Slide 2

WP within the WISDOM project

Experimental Setup

Data Analysis

Latest Results

Conclusion and Outlook

Slide 3

Slide 4

WP within the WISDOM Project:

Severe changes could be observed in the Mekong Delta:

extreme flood eventsimportant to monitor coastal

area with dense population

Test the possibility of using low elevation GNSS-Reflectometry for flood monitoring of the Mekong Delta

Develop and implement algorithms to process GPS signals into water levels

WP within the WISDOM project

Experimental Setup

Data Analysis

Latest Results

Conclusion and Outlook

Slide 5

Experimental setup:

Slide 6

Gauge

Measurement location

6 km 150 m

Experimental setup:

Two time series with two different antenna heights above the reflecting surface:

Terrace with ~10 mRoof with ~20 m

Slide 7

Experimental setup:

Two antennas (Antcom):RHCP oriented to the zenith (direct signal)LHCP tilted to the reflecting surface (reflected signal)

Slide 8

L1/L2 GPS RHCP

RHCP/ LHCPL1/L2 GPS

Direct signal

Reflected signal

Experimental setup:

Slide 9

a: GORS

b: Control unit

c: Laptop

d: External Hard Disk

WP within the WISDOM project

Experimental Setup

Data Analysis

Latest Results

Conclusion and Outlook

Slide 10

Antenna height ~ 10 m ~ 20 m

Recording time ~84 h ~60 h

Reflection events ~194 h ~ 191

Continuous phase observations > 2 min. ~26 % ~ 29 %

Continuous phase observations > 10 min ~22 % ~ 22%

Slide 11

Data Analysis:

Slide 12

Data Analysis:

Roof (~20 m)

Hotel

River

Terrace (~10 m)

Incoherent Observations Coherent Observations

Slide 13

Data Analysis:

Slide 14

Data Analysis:

River

Receiver

Reflection track

Empirical Mode Decomposition (EMD)

Method:1998 Huang [1]2008 and 2013 Hirrle [2]

Motivation:Fourier Transform assume stationarity and linearityWavelet Transform assume linearityEMD is a fully data-driven signal analysisNo need of an a priori base

Slide 15

Data Analysis:

𝑥 (𝑡 )=∑𝑖=1

𝑛

𝑥 𝑖 (𝑡 )+𝑇 (𝑡 )

Slide 16

Intrinsic Mode Functions (IMF)

Data Analysis:

𝑥𝑖𝑇 (𝑡 )

IMF

Trend

𝑥 (𝑡 ) Input signal

Slide 17

Data Analysis:

Input Signal

Slide 18

Data Analysis:

Maxima and minima

Slide 19

Data Analysis:

Cubic spline interpolation

Slide 20

Data Analysis:

Mean

Slide 21

Data Analysis:

Resulting Signal

𝑥 (𝑡 )=∑𝑖=1

𝑛

𝑥 𝑖 (𝑡 )+𝑇 (𝑡 )

Slide 22

𝑥𝑑𝑖𝑓𝑓=𝑥 (𝑡 )−𝑥𝑖 (𝑡 )=∑𝑖=2

𝑛

𝑥 𝑖 (𝑡 )+𝑇 (𝑡 )

Intrinsic Mode Functions (IMF)

Data Analysis:

𝑥𝑖𝑇 (𝑡 )

IMF

Trend

𝑥 (𝑡 ) Input signal

Slide 23

Data Analysis:

Trend

Slide 24

Data Analysis:Horizontal Reflector h = 13 m Vertical Reflector h = 1 m

Slide 25

Data Analysis:IMF 1 vs Horizontal Reflection IMF 2 vs Vertical Reflection

Completness

Slide 26

Data Analysis:PRN 12, Vietnam, Can Tho City, 28th February 2012

Freq

uenc

y

Slide 27

Freq

uenc

y

Data Analysis:PRN 12, Vietnam, Can Tho City, 28th February 2012

Slide 28

First results: EMD Observations

WP within the WISDOM project

Experimental Setup

Data Analysis

Latest Results

Conclusion and Outlook

Slide 29

Slide 30

Latest Results:

EMD

Beckheinrich J. et al, GNSS Reflectometry: Innovative Flood Monitoring at the Mekong Delta, submitted JSTARS august 2013

Slide 31

Latest Results:

Vietnam, Can Tho City, 29th February 2012

With EMD: std (1σ) = 0.05 m Without EMD: std (1σ) = 0.12 m

Slide 32

Latest Results:

Vietnam, Can Tho City, 29th February 2012

WP within the WISDOM project

Experimental Setup

Data Analysis

Latest Results

Conclusion and Outlook

Slide 33

Although the measurement were made under challenging conditions we could reach a correlation of 0.84 with the data recorded from a gauge instrument

GNSS-R could contribute to monitor water level changes of the Mekong Delta

Improvement of stochastic and functional modelDetermination of sigma reflected signals (Experiment)Include Phase Wind up effectAmplitude

Better understanding of the EMD parameters and there impact on the IMF decomposition

Slide 34

Conclusion and Outlook:

[1] Huang N.E. et al., The Empirical Mode Decomposition and the Hilbert Spectrum for non linear and non-stationary time series analysis, Proc. R. Soc. London A, (1998), pp. 903-995

[2] Hirrle A. Et al., Estimation of Multipath Parameters using Hilbert Huang Transform, ION GNSS, Nashville, Tennessee, USA, 2012

[3] Beckheinrich J. et al., GNSS Reflectometry: Innovative Flood Monitoring at the Mekong Delta, submitted at JSTARS, August 2013

Slide 35

References:

Thank you for your attention

jamila.beckheinrich@gfz-potsdam.de

Slide 36

Slide 37

First Fresnel zone, 10 m height antenna

First Fresnel zone, 20 m antenna height

Slide 38