HERACLES: EU-backed multinational project on cultural heritage preservation

In 2016, the European Unions' Research and Innovation program Horizon 2020 launched the multi-national project called HEritage Resiliance Against CLimatic Events on Site (HERACLES). The goal of this project is to design, validate and promote effective and sustainable solutions against potential threats climatic changes can bring about on the cultural heritage. For this purpose, knowledge and experiences of multiple research facilities and versatile groups of end-users in different European countries will be bundled and synergetically benefited of. In this paper, we will provide an overview about HERACLES project while a particular focus will be put on the activities concerning close-range Remote Sensing data processing. By exploiting image and laser data acquired from UAVs and from the ground, we strive for precise and reliable 3D models that are useful for representation of the scene on the desired level of detail and thus for assessing potential damages and estimating risks. From oblique UAV-borne imagery, we will obtain textured airborne 3D models using photogrammetric methods of image alignment, dense point cloud reconstruction, meshing and texturing. To provide coverage for the objects' interiors, very dense point clouds from terrestrial laser scans can be additionally captured. A triangle mesh is obtained from these points and textured by means of terrestrial high-resolution photos, whereby the registration took place using a point-based method. We identified two main challenges: first, the reconstruction results from high-resolution UAV images were not always satisfying due to a low coverage; to cope with this, extensive interactive corrections must be undertaken. Moreover, seamless merging of triangle meshes provided by aerial photogrammetric reconstruction and by terrestrial laser scans is cumbersome because of varying density and accuracy of 3D points in both meshes.