water level monitoring using the interference pattern gnss-r.ppt

WATER LEVEL MONITORING USING THE INTERFERENCE PATTERN

GNSS-R TECHNIQUE

§Remote Sensing Lab, Dept. TSC, Building D3, Universitat Politècnica de Catalunya, Barcelona, Spain and IEEC CRAE/UPC

∞SMOS-Barcelona Expert Centre, Barcelona, Spain

Tel. +34934054664, E-08034 Barcelona, Spain. E-mail: [email protected]

N. Rodriguez-Alvarez§, X. Bosch-Lluis§, A. Camps§∞, I. Ramos-Perez§, E. Valencia§, H. Park§ , M. Vall-llossera§∞

WE1.T06: Coastal and Wetlands III

IGARSS’11 – Vancouver, Canada, 24th -29th July 2011

© R.S. Lab, UPC 2011. IGARSS 2011, Vancouver, Canada, 24th-29th July 2011

WATER LEVEL MONITORING USING THE INTERFERENCE PATTERN GNSS-R

TECHNIQUE

1. INTRODUCTION

2. THE SMIGOL REFLECTOMETER

3. FUNDAMENTALS OF THE INTERFERENCE PATTERN TECHNIQUE

4. FIELD EXPERIMENT

5. RESULTS

6. CONCLUSIONS

7. ACKNOWLEDGEMENTS

INDEX

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Use of Global Navigation Satellite Signals Reflections (GNSS-R) techniques

REMOTE SENSING

Ocean Land Ice

• Altimetry• Sea State [1-5]

• Soil Moisture [6, 7] • Vegetation height [7] • Surface topography [7]

• Altimetry• Age

INTRODUCTION

[4] E. Valencia, A. Camps, X. Bosch-Lluis, N. Rodriguez-Alvarez, I. Ramos-Perez, F. Eugenio and J. Marcello, "On the Use of GNSS-R Data to Correct L-Band Brightness Temperatures for Sea-State Effects: Results of the ALBATROSS Field Experiments", IEEE Transactions on Geoscience and Remote Sensing, Accepted June 2011.

[7] Rodriguez-Alvarez, N., A. Camps, M. Vall-llossera, X. Bosch-Lluis, A. Monerris, et. al., (2011), Land geophysical parameters retrieval using the interference pattern GNSS-R technique, Geoscience and Remote Sensing, IEEE Transactions on, 49 (1), 71- 84, doi:10.1109/TGRS.2010.2049023.

[6] Rodriguez-Alvarez, N., X. Bosch-Lluis, A. Camps, M. Vall-llossera, E. Valencia, J. Marchan-Hernandez, and I. Ramos-Perez (2009), Soil moisture retrieval using GNSS-R techniques: Experimental results over a bare soil field, Geoscience and Remote Sensing, IEEE Transactions on, 47 (11), 3616 {3624, doi: 10.1109/TGRS.2009.2030672.

[1] J.F.Marchan-Hernandez, N. Rodríguez-Álvarez, A. Camps, X. Bosch-Lluis, and I. Ramos-Perez, “Correction of the Sea State Impact in the L-band Brightness Temperature by Means of Delay-Doppler Maps of Global Navigation Satellite Signals Reflected over the Sea Surface,” IEEE Transactions on Geoscience and Remote Sensing, , vol. 46, issue. 10, part 1, pp. 2914 - 2923, October 2007.

(2/14)© R.S. Lab, UPC 2011. IGARSS 2011, Vancouver, Canada, 24th-29th July 2011


TECHNIQUE

Snow

• Snow thickness [8]

[2] Valencia, E., Marchan-Hernandez, J.F., Camps, A., Rodriguez-Alvarez, N., Tarongi, J.M., et. al. “Experimental relationship between the sea brightness temperature and the GNSS-R Delay-Doppler Maps: preliminary results of the ALBATROSS field experiments, in: Proceedings of the IEEE International Geoscience and Remote Sensing Symposium 2009, vol. III. Cape Town, South Africa, pp. 741–744, 2009.

[8] N. Rodriguez-Alvarez, A. Aguasca, E. Valencia, X. Bosch-Lluis, I. Ramos-Perez, H. Park, A. Camps, M. Vall-llossera, Snow Monitoring using GNSS-R techniques. Proceedings of the IGARSS11, Vancouver, Canada, July 2011. FR4.T05: GNSS Remote Sensing in Atmosphere, Ocean and Hydrology II

[5] H. Park, E. Valencia, N. Rodriguez-Alvarez, X. Bosch-Lluis, I. Ramos-Perez, A. Camps, “A New Approach to Sea Surface Wind Retrieval from GNSS-R Measurements.” Proceedings of the IGARSS11, Vancouver, Canada, July 2011. O.2 Poster Session 2

[3] J. F. Marchan-Hernandez, E. Valencia, N. Rodriguez-Alvarez, I. Ramos-Perez, X. Bosch-Lluis, A. Camps, F. Eugenio, and J. Marcello, “Sea-state determination using GNSS-R data,” IEEE Geosci. Remote Sens. Lett., vol. 7, no. 4, pp. 621–625, Oct. 2010.

Based on he interference pattern of the GPS direct and reflected signals, after reflecting over the surface.

Objective:

GNSS-R Technique studied: The Interference Pattern Technique (IPT)

Centimeter accuracy altimetry retrieval over a water reservoir



TECHNIQUE INTRODUCTION

• Work frequency = 1.57542 GHz (GPS L1)

• Measures the interference between direct and reflected signals during all the satellite passages.

THE SMIGOL REFLECTOMETER

The Soil Moisture Interference-pattern GNSS Observations at L-band (SMIGOL) Reflectometer is the instrument implementing the IPT.

Figure 1. The SMIGOL Reflectometer architecture.

elevation angle of GPS satellite changes (Fig. 2).

• Samples @ 1 s

received interferometric power is function of the elevation angle (Fig. 3)

• Result

Figure 2. The received power is function of the GPS satellite position

• Main architecture (Fig. 1)

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Figure 2. The received power is function of the GPS satellite position

Figure 3. Received interference power as a function of the elevation angle



TECHNIQUE

THE USE OF THE IPT FOR WATER LEVEL MONITORING

21, jeRGPower

cos hGPS

4

Received interferometric power

Where :

22312

22312

1

iS

iS

eerr

eerrR

Figure 4. The SMIGOL Reflectometer basic configuration

FUNDAMENTALS OF THE INTERFERENCE PATTERN TECHNIQUE

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irrt thn

2

22

12

22sincos

2

2128

irrS

sin



TECHNIQUE

For water level retrieval it is necessary to study the effect of the variation of the h -parameter



TECHNIQUE


Figure 5. Received interference power: (a) assuming an instrument height (respect to water level) of 1 m and 3 m, and (b) zoom.

(a) (b)

• An equivalent situation was previously studied in [6]: topography retrieval of the surface.

•As it was found there, when the instrument is closer to the surface, the frequency of the oscillations vs. the elevation angle is lower than when the instrument is at a higher height.

• This height automatically translates into water level monitoring.

EFFECT OF h-PARAMETER VARIATION

0 20 40 60 80 100-15

-10

-5

0

5

10Interference power vs elevation angle

Elevation(º)

Re

cie

ved

inte

rfe

ren

ce p

ow

er(

dB

)

h = 3 m

h = 1 m

22 24 26 28 30 32

-6

-4

-2

0

2

4

6

8

Interference power vs elevation angle

Elevation(º)

Re

cie

ved

inte

rfe

ren

ce p

ow

er(

dB

)



TECHNIQUE


THE ALGORITHM FOR RETRIEVAL

• Splits the interference powers into moving windows in elevation angle containing one minimum and one maximum.

• Compute distance between minimum and maximum positions, Δθelev .

• Theoretically compute the distance for different instruments heights.

• Selects the instrument height that minimizes the error respect to Δθelev .

• Finally subtracting the initial height it is possible to monitor the variations of the water level.

FIELD EXPERIMENT



TECHNIQUE

Figure 6. The SMIGOL-Reflectometer location within the Palau reservoir

• Site: water reservoir located at Palau d’Anglesola, Lleida, Spain.

• Site coordinates 41°40'12.22"N, 0°52'31.02"E

• Size of the site 181m x 107 m

• No wind blowing in the area, surface nearly especular.

THE MEASUREMENT SITE



TECHNIQUE

Figure 7. SMIGOL-Reflectometer measuring at the water reservoir

Figure 8. SMIGOL-Reflectometer field of view

THE MEASUREMENTS

• Measurements on October 30th, 2010 (DoY 303). Ground-truth = 2.140 m measured water level.

• Measurements on December, 10th, 2010 (DoY 344). Ground-truth = 3.000 m.

• Ground-truth measured with a laser distance sensor DLR130K BOSCH by averaging 10 measurements (accuracy of 1.5 mm) with respect to the phase center of the instrument

FIELD EXPERIMENT



TECHNIQUE FIELD EXPERIMENT

Figure 8. The SMIGOL-Reflectometer measured powers and the simulated powers by applying the algorithm for (a) satellite 16 on DoY = 303 and (b) satellite 31 on DoY = 344.

THE h-PARAMETER RETIEVAL

• The SMIGOL-Reflectometer measurements were processed and the algorithm to compute the equivalent instrument height was applied to the two days of measurements

• Local maxima and local minima of measured and retrieved powers are in the same elevation angles

RESULTS



TECHNIQUE

SAT Mean level retrieved

σ rmse Δh

16 2.133 m 6 mm 9 mm 7 mm32 2.127 m 6 mm 14

mm13mm


σ rmse Δh

22 2.982 m 67 mm

88 mm

18 mm

31 2.991 m 9 mm 13 mm

9 mm

RETRIEVAL RESULTS

• DoY 303. Ground-truth = 2.140 m

• DoY 344. Ground-truth = 3.000 m

Ground-truth


Δh

3.000 m22 2.982 m 18 mm31 2.991 m 9 mm

3.006 m 28 2.997 m 9 mm

3.012 m19 3.002 m 10 mm23 3.003 m 9 mm

3.024 m 24 3.017 m 7 mm

3.036 m13 3.022 m 14 mm24 3.028 m 8 mm

3.048 m17 3.052 m 5 mm8 3.032 m 16 mm7 3.037 m 11 mm

RESULTS



TECHNIQUE

Figure 9. The water level retrieved vs the ground-truth measured. ρ = 97%, with a Pe = 1.33·10-2 and R2 =

93%.

SENSITIVITY STUDY

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CONCLUSIONS



TECHNIQUE

• The Interference Pattern Technique and the SMIGOL-Reflectometer have demonstrated to be extremely simple and yet powerful tools to monitor the water level in reservoirs and lakes.

• The algorithm developed is based on the instantaneous frequency of the oscillations of the detected interference power.

• Water level can be estimated with centimeter accuracy.

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This work by funds from the Plan Nacional del Espacio of the Spanish Ministry in the frame of the project with reference ESP2007-65567-C04-02 and also by funds from the project with reference AYA2008-05906-C02-01/ESP.

ACKNOWLEDGEMENTS



TECHNIQUE

THANK YOU

water level monitoring using the interference pattern gnss-r.ppt

Technology