The application of open-source and free photogrammetric software for the purposes of cultural heritage documentation

The documentation of cultural heritage is an essential part of appropriate care of historical monuments, representing a part of our history. At present, it represents the current issue, for which considerable funds are being spent, as well as for the documentation of immovable historical monuments in a form of castle ruins, among the others. Non-contact surveying technologies – terrestrial laser scanning and digital photogrammetry belong to the most commonly used technologies, by which suitable documentation can be obtained, however their use may be very costly. In recent years, various types of software products and web services based on the SfM (or MVS) method and developed as open-source software, or as a freely available and free service, relying on the basic principles of photogrammetry and computer vision, have started to get into the spotlight. By using the services and software, acquired digital images of a given object can be processed into a point cloud, serving directly as a final output or as a basis for further processing. The aim of this paper, based on images of various objects of the Slanec castle ruins obtained by the DSLR Pentax K5, is to assess the suitability of different types of open-source and free software and free web services and their reliability in terms of surface reconstruction and photo-texture quality for the purposes of castle ruins documentation