21 May 2015 Advances in simulating radiance signatures for dynamic air/water interfaces
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The air-water interface poses a number of problems for both collecting and simulating imagery. At the surface, the magnitude of observed radiance can change by multiple orders of magnitude at high spatiotemporal frequency due to glinting effects. In the volume, similarly high frequency focusing of photons by a dynamic wave surface significantly changes the reflected radiance of in-water objects and the scattered return of the volume itself. These phenomena are often manifest as saturated pixels and artifacts in collected imagery (often enhanced by time delays between neighboring pixels or interpolation between adjacent filters) and as noise and greater required computation times in simulated imagery. This paper describes recent advances made to the Digital Image and Remote Sensing Image Generation (DIRSIG) model to address the simulation issues to better facilitate an understanding of a multi/hyper-spectral collection. Glint effects are simulated using a dynamic height field that can be driven by wave frequency models and generates a sea state at arbitrary time scales. The volume scattering problem is handled by coupling the geometry representing the surface (facetization by the height field) with the single scattering contribution at any point in the water. The problem is constrained somewhat by assuming that contributions come from a Snell’s window above the scattering point and by assuming a direct source (sun). Diffuse single scattered and multiple scattered energy contributions are handled by Monte Carlo techniques employed previously. The model is compared to existing radiative transfer codes where possible, with the objective of providing a robust movel of time-dependent absolute radiance at many wavelengths.
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Adam A. Goodenough, Scott D. Brown, Aaron Gerace, "Advances in simulating radiance signatures for dynamic air/water interfaces", Proc. SPIE 9472, Algorithms and Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery XXI, 94720E (21 May 2015); doi: 10.1117/12.2177280; https://doi.org/10.1117/12.2177280

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