Signal Polarization Selection for GPS-IR Remote Sensing – Theoretical Analysis and Experimental Results

Qiang Chen, Daehee Won, Eric E. Small, Kristine M. Larson, Dennis M. Akos

Peer Reviewed

Abstract:	GPS interferometric reflectometry (GPS-IR) is an active remote sensing technique which can be used to estimate earth environmental parameters around the installation of the GPS antenna. Previous research efforts mainly utilize the exiting geodetic GPS network data while the performance is constrained by the characteristics of the geodetic antenna. The geodetic GPS antenna is designed to suppress the ground reflected GPS signal that contains the information about the environment. Previous studies have utilized specifically designed antenna with a particular polarization (e.g. vertical or horizontal polarizations) for various remote sensing applications. In this paper, we try to give a general discussion on the signal characteristics of various polarizations and how these characteristics can be used for remote sensing applications. We analyze the complex Fresnel reflection coefficients for all four kinds of polarizations (horizontal, vertical, right handed circular to right handed circular, right handed circular to left handed circular), and how the environmental parameters (antenna height, soil moisture) affect the reflection coefficients. For three typical remote sensing applications (snow depth, soil moisture, and vegetation growth), the suitable polarizations are discussed for each case with the conclusion that horizontal polarization is suitable for all three discussed remote sensing applications. To validate this deduction two experiments are conducted to evaluate the proposed signal selection criterion and the performance of a proposed horizontally proposed antenna in snow depth, soil moisture, and vegetation growth respectively. In the snow experiment, the observed SNR data from the customized dipole antenna show a more distinct inference pattern than the geodetic data. The estimated snow depth from the dipole antenna data is more precise than the geodetic data with a smaller 95% confidence interval. In the other field experiment, the bare soil moisture and vegetation water content (VWC) retrievals are evaluated. The amplitude of the SNR interference pattern shows a positive linear relationship with the bare soil moisture, and a negative linear relationship with the VWC in the range of 0-6.5 kg/m2. The VWC measurement range is much greater than the geodetic data (0-1 kg/m2).
Published in:	Proceedings of the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2015) September 14 - 18, 2015 Tampa Convention Center Tampa, Florida
Pages:	3958 - 3968
Cite this article:	Chen, Qiang, Won, Daehee, Small, Eric E., Larson, Kristine M., Akos, Dennis M., "Signal Polarization Selection for GPS-IR Remote Sensing – Theoretical Analysis and Experimental Results," Proceedings of the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2015), Tampa, Florida, September 2015, pp. 3958-3968.
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