<title>Automatic temperature computation for realistic IR simulation</title>

Abstract

Polygon temperature computation in 3D virtual scenes is fundamental for JR image simulation. This article describes in detail the temperature calculation software and its current extensions, briefly presented in [1J. This software, called MURET, is used by the simulation workshop CHORALE of the French DGA. MURET is a one-dimensional thermal software, which accurately takes into account the material thermal attributes of the three-dimensional scene and the variation of the environment characteristics (atmosphere) as a function of the time. Concerning the environment, absorbed incident fluxes are computed wavelength by wavelength, for each half an hour, during 24 hours before the time of the simulation. For each polygon, incident fluxes are composed of : direct solar fluxes, sky illumination (including diffuse solar fluxes). Concerning the materials, classical thermal attributes are associated to several layers, such as conductivity, absorption, spectral emissivity, density, specific heat, thickness and convection coefficients are taken into account. In the future, MURET will be able to simulate permeable natural materials (water influence) and vegetation natural materials (woods). This model of thermal attributes induces a very accurate polygon temperature computation for the complex 3D databases often found in CHORALE simulations. The kernel of MURET consists of an efficient ray tracer allowing to compute the history (over 24 hours) of the shadowed parts of the 3D scene and a library, responsible for the thermal computations. The great originality concerns the way the heating fluxes are computed. Using ray tracing, the flux received in each 3D point of the scene accurately takes into account the masking (hidden surfaces) between objects. By the way, this library supplies other thermal modules such as a thermal shadow computation tool.

High-accuracy infrared simulation model based on establishing the linear relationship between the outputs of different infrared imaging systems

“…The most widely used way is based on the temperature prediction technique, which is often adopted in the commonly used infrared scene simulation software. For example, SE-WORK-BENCH-IR [6,7], DIRSIG [8,9], OSSIM [10,11] and CAMEO-SIM [12,13] predict the temperature of the scene according to heat transfer theory, which considers the complex interaction of atmospheric effects, local meteorological conditions, solar load, temperature of the scene, emissivity of the scene, look angle, sensor location, and sensor spectral characteristics [14,15]. Another way is based on temperature inversion technique, which inverses the temperature of the scene based on the output of existing infrared imaging system (EIIS) according to the radiation transfer theory [16].…”

Study on spectral transmission characteristics of the reflected and self-emitted radiations through the atmosphere

“…A few of the developed countries possess the infrared image generation software which can deal with the targets within a certain designated region. These softwares can also be used to convert normal images to infrared images such as DIRSIG (Digital imaging and Remote Sensing Image Generation, USA, [2]), PRISM (Physically Reasonable Infrared Signature Model, USA, [3]), OKTAL (France, [4]), ShipIR/NTCS (Canada, [5]), SensorVision (Australia, [6]), CameoSim (CAMouflage Electro-Optic SIMulation, United Kingdom, [7]) and RadThermIR (USA, [8]) etc. Not all of these softwares are open to the public otherwise they are very expensive even with the limited applicability.…”