BRDF

Annual sequences of the first reprocessed albedo, bidirectional reflectance distribution function (BRDF), and nadir BRDF-adjusted surface reflectance (NBAR) products are being evaluated. BRDF model parameters (or weights) are used to compute black sky albedo at local solar noon and white sky albedo and to compute surface reflectance at a common nadir geometry. In addition to these standard resolution albedo, BRDF, and NBAR products, which are provided in the integerized sinusoidal grid projection, the BRDF parameters, black sky albedos (at local solar noon), and white sky albedos are now also being operationally produced in a global geographic projection known as the Climate Modeling Grid (CMG). These are currently available at a 0.25 degree spatial resolution, although there is community interest in a 0.05 degree resolution. In addition to the operational CMGs, coarser 0.5 degree and 1 degree resolution versions of the reprocessed albedo data have also been produced for the ISLSCP-II initiative. The global distribution of these albedos (as they vary throughout the year) are presented, as well as discussions of the most recent evaluations of the quality of the standard products.

The aim of this thesis is to investigate the applicability of a novel image synthesis technique based on Monte Carlo particle transport to daylight simulation. Many materials used in daylight simulation are specifically designed to redirect light, and as such give rise to complex effects such as caustics. The photon map technique was chosen for its efficent handling of these effects. To assess its ability to produce physically correct results which can be applied to lighting simulation, a validation was carried out based on analytical case studies and on simple experimental setups. As prerequisite to validation, the photon map´s inherent bias/noise tradeoff is investigated. This tradeoff depends on the density estimate bandwidth used in the reconstruction of the illumination. The error analysis leads to the development of a bias compensating operator which adapts the bandwidth according to the estimated bias in the reconstructed illumination.

Despite the arguments in favour of oblique photographs acquired during observer-directed reconnaissance sorties, many aerial archaeologists have extracted much valuable information from verticals generated during total coverage mapping surveys. This paper looks at one of these arguments: the issue of anisotropic surface reflectance, which is responsible for the allegedly superior rendering of (mainly) vegetation and shadow marks when observed from certain oblique viewpoints. However, after a theoretical and practical assessment of the Bidirectional Reflectance Distribution Function (BRDF) of vegetation, it becomes clear that nadir views provide a more than satisfying alternative to the extremes of an oblique approach.

The spectral and directional reflection properties of pine forest understory in Suonenjoki, Finland were measured using a newly developed transportable field goniospectrometer under direct sunlight or plant lamp. The samples represent the most typical types in Finnish forests. Large differences between species were found. Wax-leaved shrubs such as lingonberry and blueberry proved to be strong forward scatterers, whereas lichen and soft-leaved dwarf shrubs such as heather were strong backscatterers. The measured moss showed both forward and backscattering features. There were variations among the samples of the same species, but many typical features appeared consistent and reproducible. Both “pure” and mixed samples were measured, the latter showing smoother behavior than the former, that is, the strongest forward and backward features are downscaled. The results provide a starting point for an empirical understory model and a basis for development and validation of a theoretical model.

De nombreuses images terrestres georeferencees sont accessibles sur Internet, via des services d'immersion, tels que Google Street View. Afin d'ameliorer la lisibilite de ces images et permettre la juxtaposition et la comparaison de l'information qu'elles contiennent, il est necessaire de mettre en oeuvre des corrections radiometriques afin de s'affranchir des conditions d'illumination au moment de l'acquisition. Pour cela, la modelisation de la luminance recue par le capteur doit prendre en compte la diffusion atmospherique et les reflexions multiples entre objets de la scene, qui peuvent etre importantes dans le cadre de l'imagerie terrestre urbaine a tres haute resolution spatiale. Dans ce but, un simulateur de luminance au niveau du capteur, base sur le lancer de rayons, a ete developpe et valide sur des scenes simples. Le probleme inverse a resoudre est alors l'estimation de la reflectance des materiaux de la scene connaissant la geometrie de...

The irregular reflection and transmission properties of innovative fenestration allow to redirect selectively admit or block solar irradiation based on its incident direction. Compared to systems that implement adaptivity by mechanical transformations, such tailored light scattering reduces the complexity of installation, operation and maintenance as well as the impact on outward view and the aesthetical appearance of buildings. Examples of such fenestration techniques, e.g. light redirecting films and Venetian blinds featuring irregular reflection properties, are presented with their gonio-photometrically measured scattering properties. Techniques to model optically complex fenestration to support product development and planning are presented. Effects on daylight availability, glare and solar gains are demonstrated. Preliminary results indicate the potential to control and modulate rather than to block irradiation the design of buildings aiming at high comfort and energy efficiency.

The deliberate utilisation of daylight has been discussed as an outstanding element of the design of Hagia Sophia in Istanbul starting with late antique sources, and continued through the centuries up to our day. Computational simulation allows to reconstruct this illumination. This - for the first time - offers a means to relate historical descriptions and modern hypotheses with daylight as a physical phenomenon, but requires a sound methodological basis to provide valid results. Bidirectional photon-mapping is demonstrated to predict the propagation of light in the architectural space, characterised by complexity with regard to its geometry as well as the optical properties of its boundaries. The latter must be reconstructed in their original condition, eliminating modifications of the original building composition as well as deterioration of the material and finishes of building elements. The description of the latter’s irregular properties suggests data-driven modelling based on gonio-photometric measurements. Either realistic or representative description of sky conditions based on climate data or high dynamic range imaging techniques is presented and critically discussed, since it provides descriptions of the contemporary conditions. Finally, the transfer of simulation results from the physical, photometric to the perceptual domain is necessary for any interpretation in the historical sciences, and to relate the quantitative outcomes to written accounts. The authors present methods and results from the exemplary application to the case of Hagia Sophia from their ongoing research. A research agenda is proposed to close the gap between archaeological evidence, advancements in the reconstruction and computational simulation of lighting, and its potential contribution to the historical sciences in arts and building.

The goal of this study is to demonstrate the asset in using a Kalman filter to improve the spatial coherence and time consistency of surface Bidirectional Reflectance Distribution Function (BRDF) and albedo retrievals from moderate resolution sensor data sets. For this purpose, we use a simple surface model describing BRDF seasonal evolution for the land cover classes of the ECOCLIMAP