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Proceedings Paper

Images of turbulent, absorbing-emitting atmospheres and their application to windshear detection
Author(s): David W. Watt; Daniel A. Philbrick
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Paper Abstract

The simulation of images generated by thermally-radiating, optically- thick turbulent media are discussed and the time-dependent evolution of these images is modeled. This characteristics of these images are particularly applicable to the atmosphere in the 13-15 mm band and their behavior may have application in detecting aviation hazards. The image is generated by volumetric thermal emission by atmospheric constituents within the field-of-view of the detector. The structure of the turbulent temperature field and the attenuating properties of the atmosphere interact with the field-of-view's geometry to produce a localized region which dominates the optical flow of the image. The simulations discussed in this paper model the time-dependent behavior of images generated by atmospheric flows viewed from an airborne platform. The images ar modelled by (1) generating a random field of temperature fluctuations have the proper spatial structure, (2) adding these fluctuation to the baseline temperature field of the atmospheric event, (3) accumulating the image on the detector from radiation emitted in the imaging volume, (4) allowing the individual radiating points within the imaging volume to move with the local velocity, (5) recalculating the thermal field and generating a new image. This approach was used to simulate the images generated by the temperature and velocity fields of a windshear. The simulation generated pais of images separated by a small time interval. These image paris were analyzed by image cross-correlation. The displacement of the cross-correlation peak was used to infer the velocity at the localized region. The localized region was found to depend weakly on the shape of the velocity profile. Prediction of the localized region, the effects of imaging from a moving platform, alternative image analysis schemes, and possible application to aviation hazards are discussed.

Paper Details

Date Published: 1 March 1991
PDF: 12 pages
Proc. SPIE 1467, Thermosense XIII, (1 March 1991); doi: 10.1117/12.46447
Show Author Affiliations
David W. Watt, Univ. of New Hampshire (United States)
Daniel A. Philbrick, Univ. of New Hampshire (United States)

Published in SPIE Proceedings Vol. 1467:
Thermosense XIII
George S. Baird, Editor(s)

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