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Evaluation of an empirical radar backscatter model for predicting backscatter characteristics of geologic units at Pisgah Volcanic Field, California

August 15, 1994

Comparison of radar backscatter coefficients (σ°, in dB), calculated by using the empirical model of Oh et al. [1992], to σ° extracted from AIRSAR data of four geologic units at Pisgah shows that the model predicts measured σ°vv and σ°hv to within ±3 dB. The model predicts higher σ°hh than those observed. For smooth surfaces (rms height=s, s<8 cm), model results depend strongly on the accuracy of the surface measurements ( s and dielectric constant, ϵr). For rougher surfaces, the model is less dependent on the accuracy of surface characterizations. The model may be inverted to estimate s from measured σ° for surfaces with ks<3 (k = wavenumber, or 2π/λ, where λ = radar wavelength). Model inversion for a pahoehoe unit at 30° to 50° incidence angles (θ) resulted in an estimate of s to within <1 cm of the measured 3 cm. The inability of the model to estimate accurately σ°hh and the anomalously high nadir Fresnel reflection coefficients (Γo) and ϵr required in the model inversion may both be due to ∼equal co‐polarized ratios (σ°hh/σ°vv=p∼1) of the soils used to derive the model. For effective application to many geologic surfaces, for which p<1 is often observed at θ>30°, the model will require modification to include surfaces with non‐unity σ°hh/σ°vv.

Citation Information

Publication Year 1994
Title Evaluation of an empirical radar backscatter model for predicting backscatter characteristics of geologic units at Pisgah Volcanic Field, California
DOI 10.1029/94GL01253
Authors Lisa R. Gaddis
Publication Type Article
Publication Subtype Journal Article
Series Title Geophysical Research Letters
Series Number
Index ID 70202099
Record Source USGS Publications Warehouse
USGS Organization Astrogeology Science Center

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