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M. Schaepman, F. Morsdorf, R. Leiterer, N. Pfeifer, M. Hollaus, M. Disney, P. Lewis, J. Gastellu-Etchegorry, J. Brazile, B. Koetz:
"Novel reference site approach to prototyping, calibrating, and validating Earth observation data and products";
Talk: American Geophysical Union (AGU) Fall Meeting 2012, San Francisco, CA, USA (invited); 2012-12-03 - 2012-12-07.

Much of global change is driven by feedback mechanisms taking place at spatial and temporal scales that are smaller than those currently incorporated in models. This severely limits our ability to predict, mitigate and adapt to environmental change at local and regional scales. Ideally, global modelling, reference sites and data will gradually converge to spatial and temporal scales where processes at their characteristic length scale can be compared, Ultimately; scale invariant observations and products would be the goal. But because of the inherent nature of a changing environment, spatio-temporal homogeneity of reference sites will remain a main concern. Globally distributed sites with naturally changing homogeneity and biome cover are of fundamental importance to understand potential bias errors in retrieval algorithms, amongst other benefits. We propose a new site concept using a highly detailed description of vegetation based on terrestrial and airborne laser scanning, extensive optical properties measurements as well as airborne imaging spectrometer data acquisition in combination with both, 1D and 3D radiative transfer models. Effects of horizontal and vertical heterogeneities and asymmetrical structure of vegetation and high temporal dynamics can be simulated and used in algorithm development, calibration and validation procedures. The approach allows comparison with heritage algorithms and products, and will support estimates of scale invariance for all spatial, spectral, and temporal dimensions. The site design is further using standards, allowing stage 1 & 2 validation according to CEOS/LPV (Committee on Earth Observation Satellites/ Land Product Validation Subgroup) recommendations as well as supporting the Quality Assurance Framework for Earth Observation (QA4EO) of the ESA/CEOS Cal/Val initiative. We demonstrate feasibility of the approach using the `Laegeren´ site (temperate deciduous forest, with dominant beech trees; 47°28'42.0" N; 8°21'51.8" E, 682 m asl, Switzerland). We conclude on the use of very detailed reconstruction of vegetation sites and recommend a scheme to establish standards for a larger network of sites.