Atmospheric model used in the Orthorectification Module for ENVI

The Orthorectification Module in ENVI includes an intersection model that takes into account deviation caused by atmospheric refraction. To correct for this, an atmospheric model is applied. This Help Article describes the atmospheric model mentioned in the ENVI Orthorectification Module Whitepaper.

The atmospheric model used is described in section 3.4.1 (Atmospheric Refraction) of Manual of Photogrammetry 5th ed. 2004. Specifically it uses equation 3.147 in this section which only uses two parameters, and assumes a standard atmospheric density profile (Airforce ARDC 1959).





where H is the flying height above mean sea level and h is the terrain elevation (km) and K is in radians. K is the amount of refraction for a ray at 45°. To generalize for other angles,





where alpha is the angle a ray makes with the vertical and delta alpha is the displacement associated with refraction. This systematic correction is them used with the ground to image function to correct the image coordinates.

Review on 12/31/2013 MM