The preservation of memory to restore the matter. Approaches to survey and documentation of heritage at risk

Cultural Heritage under risk or in emergency conditions is an increasingly common contingency. Critical issues related to preservation highlight the topic of conservation of matter, not only as transmission of heritage to future generations but also as a search for new intervention strategies and design of the existing, and conservation of memory, as cultural choice to protect those intangible values socially shared. The survey and documentation of heritage become the essential support to the achievement of higher levels of knowledge and awareness: the possibility of gaining archives of the "geometric memory" of the historical and architectural heritage opens up new possibilities for the protection, conservation, restoration, up to the controversial discussion about "where it was but not as it was". The paper presents a comparison among different experiences of survey and documentation of heritage in states of emergency or hazardous conditions through different methodological approaches. From the survey of city centers affected by the earthquake in Italy to documentation of urban transformations of Jodhpur, India; from the survey of the archaeological excavations in the heart of Mexico City, up to new strategies of documentation and conservation of Brazilian modernist architecture.