In this work we consider atmospheric refractive bending and its effects on long-range imaging along a horizontal path. Refraction can impact the ability of a remote sensing or image system to accurately locate objects and determine their apparent proportions. We use a low-cost commercial camera operating in a time-lapse mode for refraction studies and have been recording images of a building that is 15.3 km west of the camera. Based on the paraxial ray equation, a solution for ray height and angle is obtained for a refractive index profile with curvature. A curved index profile can produce the effects of towering (stretching) and stooping (compression). The curvature parameter for the average atmospheric index profile between the camera and target can be derived from an analysis of the images collected by the camera system. We show example images where the building (33 m height) appears to stretch by 5.1 m and calculate a refractive index curvature parameter of 6.0x10^-5 m^-2.

Date Published: 13 May 2016
PDF: 8 pages
Proc. SPIE 9833, Atmospheric Propagation XIII, 98330D (13 May 2016); doi: 10.1117/12.2224294

Published in SPIE Proceedings Vol. 9833:
Atmospheric Propagation XIII
Linda M. Thomas; Earl J. Spillar, Editor(s)