Documenting lost heritage. The experience of the survey of architectures damaged by the earthquake in the Emilia area, Italy.

One year ago, the earthquake that devastated a wide architectural heritage in the Emilia area, in Northern Italy, gave rise to a series of surveys and investigations aimed at both documenting a lost or seriously compromised heritage and at recording information that can be used by different operators (i.e. fire departments, civil protection, engineers, architects, urban planners) and for different uses in different times, concerning the development of safety, recovery, restoration or demolition programs. The characteristics of that particular earthquake damaged a wide variety of buildings concerning both historical centers, rural buildings and recent buildings, that were built using different technologies. The devastation also involved buildings in which documentation on built heritage was collected, such as, for example, land registries and other historical archives. As a consequence, the impossibility to rapidly recover the previously acquired documentation or its unavailability gave rise to extensive survey campaigns. Besides the urgency of developing safety programs, in some cases, these survey campaigns were also motivated by the purpose of collecting information on heritages that share common architectural composition and structural characteristics and therefore belong to specific building typologies. These kinds of investigations are particularly useful in case studies such as, for example, rural buildings, that were not previously accurately and documented in detail. In other cases, large scale documentation was mandatory in order to conduct a census of specific heritages, such as, for example, worship buildings, and their location on the territory, in order to plan their reconstruction, demolition or restoration based on actual needs and real possibilities of intervention. The aim of this contribution is to show how digital methodologies and technologies can be used as an indispensable practice in order to produce graphic documentation about an architectural heritage that has been destroyed or severely damaged by a natural disaster. The presented case studies belong to a repertoire that ranges from single buildings to wider complexes that were selected for their historical and cultural importance and for the urgency of the development of intervention plans. In all case studies, the aim of surveys was to collect the most detailed and accurate information compatibly with the reduced possibility of access to unsafe buildings. In particular, most of them have been surveyed just from the outside, using fast and non contact survey methodologies, while documentation of inside spaces was collected through photographic repertoires, preexisting documentation or specific targeted investigations. In some cases, documentation was also integrated and completed thanks to accurate descriptions that were reported by people who lived those spaces. All accessible areas were acquired mainly using laser scanners; in some cases, when accuracy and definition were not priority tasks, the indirect measurement approach supported by orthophotos was adopted instead of a range-based one. In other cases, a structure from motion approach was used in order to quickly reconstruct the integrity of collapsed elements.