# A Methodical Approach to 3D Scanning of Heritage Objects Being under Continuous Display
## 2 Study Background  
In situ digitization of heritage objects is usually affected by the following difficulties: the necessity to bring and set-up the equipment needed during digitization; limited access to heritage objects and safety of their extraction; as well as ongoing tourist traffic. Digitization of tangible cultural heritage objects can be implemented in many ways, in terms of technology as well as conditions for data acquisition and access to heritage site facilities. [PERSON] et al. in [17] present a variety of technological solutions suitable for 3D digitization. Most of the solutions are based on aerial and terrestrial photogrammetry, although the role of terrestrial laser scanning usage in data acquisition is mentioned as well. The authors also give examples of 3D reconstruction of architectural structures, i.e., the remains of Las Higueras city (Argentina) and historical buildings such as the Rohan Palace facade, the Catholic church of St-Pierre-le-Jeune, the Josephine Pavilion in Strasbourg (France), the Byzantine Land Walls of Istanbul (Turkey) or the Temple of the Sacred Tooth Relic at Kandy (Sri Lanka). Architectural details were acquired by means of a hand-held scanner using Artec's structured light technology. However, the authors did not pay attention to the aspects related to local (in situ) conditions concerning (influencing) the digitization process, despite the fact that these objects were frequently visited by tourists. [PERSON] et al. in [18] present various theoretical aspects regarding the issues of 3D digitization of architectural and museum objects, as well as many practical implementations. Some of the described devices have significant limitations in their use in situ, e.g., stationary chamber scanners (Roland PICZA 3D Laser Scanner LPX-600) have a small working space and cause difficulties in transport due to their large weight and size. Another presented device--ZScanner (r) 700, which is a hand-held laser scanner, requires placing markers on the surface of a digitized object, which is usually not allowed in the case of historic objects [19]. A confirmed drawback of these devices is the inability to collect information about the texture of scanned objects, which limits their use in transferring cultural heritage to the digital world. [PERSON] et al. in [20] present a low-cost 3D data acquisition system for small objects using a set of Kinect v2 devices cooperating with the open source LiveScan3D software. Unfortunately, there are a lot of cases requiring more professional solutions in terms of precision, range, durability, ability to deal with environmental factors. [PERSON] et al. in [21], apart from the above-mentioned aspects, deal with the topic of 3D reconstruction. Practical implementation of activities concerning the 3D digitization of heritage objects can be found in many other works, to mention creating virtual spaces [22; 23] or the scanning of: the Hercules statue from the Antalya Museum in Turkey and the Khmer head from the Rietberg Museum in Zurich [24]; a complex of historic buildings in Malacca, Malaysia, declared a UNESCO World Heritage Site in 2008 [25]; artifacts in the area of Sarmisegetuza Regia archaeological site [26]. Nevertheless, in the opinion of the authors of this article, the topic of 3D scanning of heritage objects being under continuous display was not addressed as it needs to be. What is more, there is a wide agreement that there are not enough free databases that could be used for comparative tests of algorithms and procedures [17; 27; 28; 29]. Few works address issues related to accessing heritage objects and dealing with particular conditions of heritage sites subjected to 3D scanning. [PERSON] et al. in [5] present many problems related to removing objects to be scanned from an exhibition and preparing them for 3D scanning process. In order to extract the objects from the showcases from the 1970s, several museum employees offered their cooperation. Some objects needed re-forming after being extracted.