Nowadays the continuous development of Spatial Data Infrastructures (SDIs) provides a favourable context for environmental and urban management.It is now largely expected that SDIs should contribute to broader goals such as economic development, social stability, good governance and sustainable management of the environment. However, the real contribution of SDIs is still difficult to evaluate apart from some general positive statements which are not demonstrated or even supported by objective findings. The problem is large as SDIs are complex distributed frameworks that involve a large number of users and organisations that are likely to produce, manage, analyse and exchange geographical information at different levels of abstraction and scale. The aim of this research is to make some progress towards the analysis of SDIs usages as well as their evolution over time. We believe that, by improving geographical information access at large, favouring collaborative data production and information exchanges, SDIs appear as a particularly relevant research topic to study social and spatial dynamics related to GI produced by a large spectrum of users from experts to citizens. Monitoring the main properties and evolutions of SDIs usage and GI usage should provide some relevant qualitative and quantitative indicators, which, when combined with other dimensions of GI (semantics, data quality, legal issues...) should feed on-going discussions related to Geographic Information Observatories.