DocumentCode :
1023416
Title :
Microwave Attenuation Properties of Vegetation Canopies
Author :
Ulaby, Fawwaz T. ; Wilson, Edward A.
Author_Institution :
Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109
Issue :
5
fYear :
1985
Firstpage :
746
Lastpage :
753
Abstract :
A major impediment to the understanding and modeling of propagation through and backscattering and emission from vegetation canopies has been the lack of canopy attenuation data as a function of frequency, incidence angle, and polarization configuration. This paper presents the results of attenuation experiments conducted for canopies of winter wheat and soybeans in the late spring and early summer of 1984. Attenuation data were acquired at 1.55, 4.75, and 10.2 GHz for horizontal and vertical polarizations at incidence angles near 20° and 50°. In addition, wheat decapitation and soybean defoliation experiments were conducted to evaluate the relative importance of different canopy constituents (such as heads, leaves, and stalks) to the total canopy attenuation. The measured data were compared to calculations based on a model that treats the stalks as parallel elements of a uniaxial crystal and the leaves and branches as randomly oriented disks and needles, respectively. Very good agreement was obtained between theory and experimental observations for the soybean canopy for both polarizations and for the wheat canopy for vertical polarization; however, the model consistently underestimated wheat attenuation (relative to the data) for horizontal polarization. This deficiency of the model is attributed to the fact that it considers all the stalks to be vertically oriented, whereas in reality the stalks exhibit an orientation distribution, although it is centered around the vertical direction.
Keywords :
Attenuation measurement; Backscatter; Biomass; Impedance; Microwave frequencies; Microwave propagation; Polarization; Radar scattering; Springs; Vegetation;
fLanguage :
English
Journal_Title :
Geoscience and Remote Sensing, IEEE Transactions on
Publisher :
ieee
ISSN :
0196-2892
Type :
jour
DOI :
10.1109/TGRS.1985.289393
Filename :
4072369
Link To Document :
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