Presentation is loading. Please wait.

Presentation is loading. Please wait.

08.04.10 GPS Multipath and its Relation to Near-Surface Reflectivity Slide 1/14 Natasha Whitney Harvard University National Geodetic Survey/NOS Mentor:

Similar presentations


Presentation on theme: "08.04.10 GPS Multipath and its Relation to Near-Surface Reflectivity Slide 1/14 Natasha Whitney Harvard University National Geodetic Survey/NOS Mentor:"— Presentation transcript:

1 08.04.10 GPS Multipath and its Relation to Near-Surface Reflectivity Slide 1/14 Natasha Whitney Harvard University National Geodetic Survey/NOS Mentor: Andria Bilich

2 08.04.10 Forecast Slide 2/14 Can we use reflected GPS satellite signals (multipath errors) to detect nearby precipitation events and soil moisture content?

3 08.04.10 Outline Slide 3/14 Background Methodology Results Further work Summary Acknowledgement

4 08.04.10 Background Slide 4/14 Signal to noise ratio (SNR) Ground reflectivity & soil moisture content Geometric optics: (i)Specular reflection (ii)Ray tracing d  =2  2hcosθdθ dt dt

5 08.04.10 Methodology Slide 5/14 Large metal experiment: Simplify various parameters Effective penetration depth (d) Polarization (all Left Hand Circular) Reflect signal amplitude attenuation

6 08.04.10 Methodology Slide 5/14 Signal Amplitude (A) Antenna gain Effective reflector height (h) Phase center offset Governing equation SNR MP =A M cos(  +  o )

7 08.04.10 Results Slide 7/14 Observations: -non-sinusoidal @ low  -noisy @ midrange  -suppressed at high  Relevant range of  ?

8 08.04.10 Results Slide 6/14 Fast Fourier Transform (FFT): Eff. reflector height? Max amp? Wavelet Analysis: Phase center offset changes?

9 08.04.10 Results Slide 8/14 Initial modeling attemptsRole of surface roughness

10 08.04.10 Results Slide 9/14 Sensitivity of interference fringes to sea surface roughness for L2 signal Second modeling attempt

11 08.04.10 Results Slide 10/14 Predicted Antenna Gain Experimental results: Effect of 180  rotation

12 08.04.10 Results Slide 11/14 Antenna tilted 90  Effect of tilt on raw SNR signal

13 08.04.10 Further Work Slide 12/14 1.Reduce edge effects: reduce discontinuity of induced electric field of conducting plane 2.Continue tomographical scan: use azimuthal, boresite, and tilt rotations to assess amplitude, phase center, and effective reflector height

14 08.04.10 Summary Slide 13/14 Hypothesis v. Results: How useful was the large metal experiment? Calibration potential: Which parameters can provide real, physical information? Bigger picture: In-situ soil moisture network

15 08.04.10 Acknowledgements Slide 14/14 Thank you NGS and ESRL team at Skaggs: Valery Zavorotny Felipe Nadinsky [TKTK] Kristine Larson Andria Bilich Kyle [TKTK] Resources used: VALERY PRES. 1.K. M. Larson, E. E Small, E. Gutmann, A. Bilich, J. Braun, and V. Zavorotny, “ Use of GPS receivers as a soil moisture network for water cycle studies, ” Geophys. Res. Lett. vol.. 35, no. DOI:10.1029/2008GL036013, p. L24405, 2008. 2.K. M. Larson, J. J. Braun, E. E. Small, V. U. Zavorotny, E. Gutmann, and A. L. Bilich, “ GPS multipath and its relation to near surface soil moisture content モハ IEEE J. Sel. Topics Appl. Earth Obs. Remote Sens.” vol. 3 no. 1, Mar. 2010. 3.V. U. Zavorotny, K. M. Larson, J. J. Braun, E. E. Small, E. D. Gutmann, and A. L. Bilich, “ A Physical model for GPS Multipath Caused by Land Reflections: Toward Bare Soil Moisture Retrieval ”, IEEE ハ J. Sel. Topics Appl. Earth Obs. Remote Sens. Vol. 3, no. 1, Mar. 2010. 4.Bilich, A. L., "Improving the Precision and Accuracy of Geodetic GPS: Applications to Multipath and Seismology". Ph.D. dissertation, University of Colorado, 2006.

16 08.04.10 Backup Slides Team survey topography at Table Mountain Experimental Site


Download ppt "08.04.10 GPS Multipath and its Relation to Near-Surface Reflectivity Slide 1/14 Natasha Whitney Harvard University National Geodetic Survey/NOS Mentor:"

Similar presentations


Ads by Google