It is important to understand the relationship between a citizen observatory and the previously introduced concept of participatory campaigning. Generally speaking, a citizen observatory collects, analyses, and evaluates a specific type of data (e.g. environmental noise, water polution, etc.). To collect this data, each observatory has one dedicated mobile data collection app. Within each citizen observatory, users can deploy campaigns to aggregate data for a particular goal or concern. Campaigns are only interested in a subset of the observatory data, and thus describe how the observatory data should be filtered, processed, and aggregated. Note that a citizen observatort does not necessarily collect data only through campaigns. The idea of a citizen observatory is usually to obtain publicly available data that stakeholders can use in their policy making. It is therefore perfectly possible that stakeholders merely use the citizen observatory to create visualisations using the available open data without actually running a campaign themselves. Citizen observatories also serve as an information hub for citizens. For example, an individual user might consult the citizen observatory data to get an idea of the noise pollution that he is exposed to in his daily life.