Automated analyses of degradations

If the digital acquisition of a monument aims in the first place at exhaustively determine its geometry, current sensors and data processing software also facilitate the extraction of information related to the different pathologies of degradation of the digitized surfaces. The cartographies thus generated can be used by restorers and curators.

A methodology has been developed by our company that uses morphological and chromatic analysis of the data to produce a preliminary automated mapping of the pathologies of the facings, according to the rules defined by ICOMOS.

In 2018, Archéotech was commissioned to carry out a complete survey of Lausanne Cathedral. The interior and exterior were measured by laserometry and photogrammetry. The data collected allowed the development of an application for the automated detection of various stone pathologies. Thanks to the analysis of the micromorphology, colorimetry and laser photometry of the surfaces, the degradations of the exterior facings of the cathedral could be mapped and quantified, with particular attention to the damage due to water runoff, by determining the biological colonisations, crusts and gaps.

Facade reproduced in 3D of Lausanne Cathedral (VD), colourisation of the points from photographs

Roughness analysis

Roughness analysis: we can see the erosion, the holes or the missing parts appear

Intensity analysis: help understand crusts, sediments and patinas

Thematic analysis by colour: creation of RGB maps

Thematic analysis by colour: help understand des chromatic alterations

Thematic analysis by colour: help understand crusts and sediments on the surface

Thematic analysis by colour: help understand mosses and lichens

Typologies of the detected degradations ordered according to the glossary of the ICOMOS

The result of the analysis on the cathedral of Lausanne: in red, the crusts - in blue, the gaps - in green, the biological colonisations