2. How do you acquire the essential prior knowledge of the site and its surroundings?

This prior knowledge requires a site visit, from which documentary, historical and vulnerability studies can be carried out.

This knowledge is an essential prerequisite for field measurement campaigns (see next step). It provides the information needed to optimize the size of the measurement campaign. The campaign must be sufficiently large to provide an adequate response to the problem, while remaining proportionate and adapted to the risks involved.

The process for acquiring this prior knowledge is detailed in the "Site diagnosis" document approved by the MEEDDAT in February 2007.