Don’t touch: just watch! The fluorescence lidar technique as a non invasive tool for cultural heritage diagnostics

Since our childhood we have been told "don’t touch, just watch!". This sentence fits particularly well both the cultural heritage world and the remote sensing technique. Here we describe the experience gained with a remote sensing instrument (a fluorescence lidar) that has been applied for the diagnostics of historical monuments. Fluorescence lidar imaging is a non-invasive technique that extends the application of the laser induced fluorescence technique to the outdoor environment and combines it with the advantages provided by imaging. Fluorescence imaging has been proven useful for the detection of biodeteriogens, of protective coatings and for the characterisation of masonry materials on the basis of their fluorescence. The imaging capabilities of lidars have further enhanced their potential for the diagnostics of the cultural heritage since they offer a simpler data presentation providing false-colour maps as a support tool for conservators and stakeholders.