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Sea surface simulation in the infrared modeling and validation

 
: Schwenger, Frederic; Repasi, Endre

:
Postprint urn:nbn:de:0011-n-1024892 (879 KByte PDF)
MD5 Fingerprint: ca72a108b5abbe1b8b315b0107edebc6
Copyright 2006 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
Erstellt am: 26.9.2009


Watkins, W.R. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Targets and backgrounds XII. Characterization and representation : 17 - 18 April 2006, Kissimmee, Florida, USA
Bellingham, WA: SPIE, 2006 (Proceedings of SPIE 6239)
ISBN: 0-8194-6295-0
ISBN: 978-0-8194-6295-4
Paper 62390J, 14 S.
Conference on Targets and Backgrounds <12, 2006, Kissimmee/Fla.>
Englisch
Konferenzbeitrag, Elektronische Publikation
Fraunhofer IOSB ()

Abstract
A physics based 3D simulation of sea surfaces is presented. The simulation is suitable for the pre-calculation of detector images for an IR camera. Synthetic views of a maritime scenario are calculated in the MWIR and LWIR spectral bands and the images are compared with data collected in a field trial.
In our computer simulation the basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. Sea surface animation is introduced by time dependent control of the basic statistics. Choppy waves are included into the model to improve the realism of the rough sea. To predict the view of a thermal camera the sea surface radiance must be calculated. This is done with respect to the emitted sea surface radiance and the reflected sky radiance, using either MODTRAN or a semi-empirical model. Slope-shadowing of the sea surface waves is considered, which strongly influences the IR appearance of the sea surface near the horizon. MWIR and LWIR simulations are shown of sun glint as well as of whitecaps which depend upon wind velocity.
For validation purposes appropriate data sets (images and meteorological data) were selected from field measurements. A simple maritime scenario including a floating foreground object has been prepared and views of two different thermal imagers, similar to those used in the field trials, have been simulated. The validation is done by visual inspection of measured and simulated images and in addition by numerical comparison based on image statistics. The results of the comparison are presented. For an accurate reflectance calculation it is necessary to consider the maritime sky. The model is improved by inclusion of a static two-dimensional cloud layer. The cloud distribution adjusted to measured data with respect, e.g. to power spectral density and temperature distribution.

: http://publica.fraunhofer.de/dokumente/N-102489.html