Uncertainty propagation in chained web based modeling services: the case of eHabitat

eHabitat is a Web Processing Service (WPS) designed to compute the likelihood of finding ecosystems wi th similar conditions. Starting from a reference area, typical ly protected area, one can compute for each pixel of a region of interest the probability to find a combination of a set of predefined environmental indicators that is similar to the one observed in the reference area using the Mahalanobi s distances to the mean and covariance of these ind icators. Inputs to the WPS are thus the reference polygon and a set of environmental indicators, typically thematic ge ospatial “layers”, which can be discovered using standardised ca talogues. The outputs can be tailored to specific e nd user needs in terms of data format and data resolution. Because t hese input layers can range from geophysical data c ptured through remote sensing to socio-economical indicato rs, eHabitat is exposed to a broad range of differe nt types and levels of uncertainties which are inevitably propagated through the service (see e.g. Heuvelink, 1998). Potentially chained to other services to perform ecological for ecasting, for example, eHabitat would be an additio nal component further propagating uncertainties from a potentiall y long chain of model services. Such a configuratio n of distributed data and model services as envisaged by initiatives such as the “Model Web” from the Group on Earth Ob servations, to be of any use to policy or decision makers, requ ir s from users clear information on data uncertain ties. The development of such an Uncertainty-Enabled Model Web is the scope of the UncertWEB project which is promoti ng interoperability between data and models with quantif ied uncertainty and building a framework on existin g open, international standards. It is the objective of this paper to illustrate a few key ideas behind UncertWe b using eHabitat to discuss the main types of uncertainties the WPS has to deal with and to present the benefits of the use of the Un-