<p>Whether your data is spaceborn, airborne, or ground measurements, you will need to find out the appropriate equations and coefficients to convert data DN values to radiance.&nbsp; These&nbsp;should be available from your data provider since the equations to use are not all the same.&nbsp; Most use some form of: </p> <p>Radiance (of some unit, often W/(m^2*sr*um))&nbsp;= DN * gain + offset </p> <p>but some require you incorporate the band pass and&nbsp;some are just simple scale factors that you apply to the DN.</p> <p>Once you have radiance, then you can convert it to reflectance using a standard equation, unless your data provider gives you simple scale factors to apply directly to the DN that convert to reflectance (such is the case with Landsat-8 data).&nbsp; These equations are discussed in the ENVI Help under <a href="http://file:///C:/Program%20Files/Exelis/ENVI53/help/Content/PreprocessImagery/PreprocessImagery.htm" target="_blank" rel="nofollow">Preprocessing</a> &gt; <a href="file:///C:/Program%20Files/Exelis/ENVI53/help/Content/PreprocessImagery/RadiometricCorrectionTools.htm" class="MCBreadcrumbsLink">Radiometric Correction Tools</a> &gt; Radiometric Calibration.&nbsp; Your data provider should be able to provide you some of the parameters for this such as solar irradiance and elevation.</p>

<p>Thanks Mari - apparently the imagery I have is corrected to surface reflectance - but they cannot account for bidirectional reflectance and scattering- makes sense.&nbsp;</p> <p>I also have issues with illumination inconsistencies across my mosaics. This is from partial cloud cover during the flight missions. Any way to batch process histogram matching/illumination equalization in ENVI? Thanks &nbsp;</p>

The seamless mosaic tool includes the ability to include seam lines and perform feathering and&nbsp;color/histogram matching.&nbsp; You can try these tools and they also have associated Tasks that can be used for batch processing (<a name="kanchor903"></a>ENVIBuildMosaicRasterTask).