<?xml version='1.0' encoding='utf-8'?>
<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:creator>Lisa R. Gaddis</dc:creator>
  <dc:date>1994</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;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°&lt;/span&gt;&lt;sub&gt;vv&lt;/sub&gt;&lt;span&gt;&amp;nbsp;and σ°&lt;/span&gt;&lt;sub&gt;hv&lt;/sub&gt;&lt;span&gt;&amp;nbsp;to within ±3 dB. The model predicts higher σ°&lt;/span&gt;&lt;sub&gt;hh&lt;/sub&gt;&lt;span&gt;&amp;nbsp;than those observed. For smooth surfaces (rms height=&lt;/span&gt;&lt;i&gt;s&lt;/i&gt;&lt;span&gt;,&amp;nbsp;&lt;/span&gt;&lt;i&gt;s&lt;/i&gt;&lt;span&gt;&amp;lt;8 cm), model results depend strongly on the accuracy of the surface measurements (&amp;nbsp;&lt;/span&gt;&lt;i&gt;s&lt;/i&gt;&lt;span&gt;&amp;nbsp;and dielectric constant, ϵ&lt;/span&gt;&lt;sub&gt;r&lt;/sub&gt;&lt;span&gt;). For rougher surfaces, the model is less dependent on the accuracy of surface characterizations. The model may be inverted to estimate&amp;nbsp;&lt;/span&gt;&lt;i&gt;s&lt;/i&gt;&lt;span&gt;&amp;nbsp;from measured σ° for surfaces with&amp;nbsp;&lt;/span&gt;&lt;i&gt;ks&lt;/i&gt;&lt;span&gt;&amp;lt;3 (&lt;/span&gt;&lt;i&gt;k&lt;/i&gt;&lt;span&gt;&amp;nbsp;= 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&amp;nbsp;&lt;/span&gt;&lt;i&gt;s&lt;/i&gt;&lt;span&gt;&amp;nbsp;to within &amp;lt;1 cm of the measured 3 cm. The inability of the model to estimate accurately σ°&lt;/span&gt;&lt;sub&gt;hh&lt;/sub&gt;&lt;span&gt;&amp;nbsp;and the anomalously high nadir Fresnel reflection coefficients (Γ&lt;/span&gt;&lt;sub&gt;o&lt;/sub&gt;&lt;span&gt;) and ϵ&lt;/span&gt;&lt;sub&gt;r&lt;/sub&gt;&lt;span&gt;&amp;nbsp;required in the model inversion may both be due to ∼equal co‐polarized ratios (σ°&lt;/span&gt;&lt;sub&gt;hh&lt;/sub&gt;&lt;span&gt;/σ°&lt;/span&gt;&lt;sub&gt;vv&lt;/sub&gt;&lt;span&gt;=p∼1) of the soils used to derive the model. For effective application to many geologic surfaces, for which p&amp;lt;1 is often observed at θ&amp;gt;30°, the model will require modification to include surfaces with non‐unity σ°&lt;/span&gt;&lt;sub&gt;hh&lt;/sub&gt;&lt;span&gt;/σ°&lt;/span&gt;&lt;sub&gt;vv&lt;/sub&gt;&lt;span&gt;.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1029/94GL01253</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>American Geophysical Union</dc:publisher>
  <dc:title>Evaluation of an empirical radar backscatter model for predicting backscatter characteristics of geologic units at Pisgah Volcanic Field, California</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>