Seasonal polarimetric measurements of soil moisture using tower-based GPS bistatic radar
Seasonal polarimetric measurements of soil moisture using tower-based GPS bistatic radar
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DOI：
10.1109/igarss.2003.1293916
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发表时间：
2003-07
期刊：
影响因子：
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通讯作者：
V. Zavorotny;D. Masters;A. Gasiewski;B. Bartram;S. Katzberg;P. Axelrad;R. Zamora
中科院分区：
文献类型：
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作者：
V. Zavorotny;D. Masters;A. Gasiewski;B. Bartram;S. Katzberg;P. Axelrad;R. Zamora
描述了GPS l波段（L1, /spl λ / = 19 cm）表面反射测量的结果。测量是在2002年夏季到秋季期间使用300米高的ETL博尔德大气观测台（BAO）塔进行的。在本实验中，首次使用双基地反射机会信号对固定位置的裸土湿度进行了季节性测量。采用了几种具有不同增益和极化灵敏度的接收天线。双基地表面散射的理论模型表明，反射波形的幅度和宽度取决于土壤的介电常数、植被覆盖和土壤粗糙度。通过在低矮草地上的固定塔上观察，反射区域的粗糙度保持不变，因此信号的变化与介电常数的变化有关，因此与土壤湿度有关。为了研究反射信号对土壤水分的极化敏感性，使用了4根具有完全圆极化和正交极化灵敏度的端射（/spl sim/ 12 dB）天线。高增益天线增加了接收动态范围，减少了表面多径无线电波干扰。利用GPS多极化反射数据反演土壤水分，并与原位土壤水分测量结果进行了比较。
The results of GPS L-band (L1, /spl lambda/ = 19 cm) surface reflection measurements observed using multiple polarizations and receiving antenna gains are described. The measurements were performed using the 300 m tall ETL Boulder Atmospheric Observatory (BAO) tower during summer through fall of 2002. In this experiment, the first seasonal measurements of bare soil moisture from a stationary location using bistatic reflection of signal of opportunity were performed. Several receiving antennas offering various gain and polarization sensitivities were used. Theoretical modeling of bistatic surface scattering shows that the magnitude and width of the reflected waveform depend on the dielectric permittivity of the soil, vegetation cover, and soil roughness. By observing from a fixed tower over low grass, the roughness of the reflecting area remains constant, hence variations in the signal are uniquely related to changes in the dielectric permittivity, and therefore, to soil moisture. To investigate polarization sensitivity of the reflected signal to soil moisture, four endfire (/spl sim/ 12 dB) antennas with complete circular and orthogonal polarization sensitivities were used. The high-gain antennas increased the received dynamic range and reduced surface multipath radio wave interference. Seasonal retrievals of soil-moisture content from multi-polarization GPS reflection data is presented and compared with in-situ soil moisture measurements.