## 2 Rock Art Documentation  
The issue of protection of various types of historical and cultural properties, apart from defensive ones, including sacred and secular structures and such objects as petroglyphs, inscriptions or stone monuments, has been taken up by state and local authorities in all corners of the world: Asia (Mongolia [10], Russia [11], United Arab Emirates [12]), Africa [13], North America [14], South America (Brazil [15], Peru [16]), Australia [17; 18] and Europe (Spain [19; 20; 21; 22; 23], Sweden [24; 25; 26], Italy [27; 28], UK [29] and France [30]). For example, according to the inventory conducted in Mongolia [10], petroglyphs and other rock art constitute 14% (i.e., 3261 artefacts) of the monuments in this country. Research on rock art (petroglyphs) is carried out primarily by domestic researchers working in \"their backyard\", although there are instances of highly advanced international collaborations [12], for example a three-year project led by Departamento de Ingenieria Topografica y Cartografia of the Universidad Politecnica de Madrid (Spain) in the Emirate of Sharjah, United Arab Emirates. The activities carried out currently take three main directions, apparently not always interconnected: cultural research, research on data acquisition methods, and protection and sharing. The basic direction of research is the analysis of petroglyphs in terms of culture, e.g., the assessment of zoomorphic and pragmamorphic artefacts in the context of the existence of certain rhetorical figures--assigning the properties of animals and objects to humans [24], or in the aspect of interpreting rock narratives in the context of the theory of migration and diffusion of ideas, along with using ethnographic and folklore materials [11]. The problem of dating rock sites has not yet been solved in numerical terms. It is easier to build a reliable chronological framework that takes into account aspects such as group mobility or emerging cultural networks [23]. In recent years, many studies have presented a description of various modern technologies for data acquisition in conducted research. In works [24; 29] various technologies used to document petroglyphs are traced, from the oldest, often called traditional ones, which are now less and less used, such as frottage, tracing and drawing. All these technologies maintain fairly precise dimensions of the rock drawings, although they have many disadvantages: they poorly reflect spatial surfaces, are very time-consuming, are not suitable in cold and humid climates, and largely depend on the experience of the person carrying out the work. There is no reference to dimensions in the methods based on single photos obtained with conventional or digital photography, taken without placing additional markers or rules on the objects. In the last two decades, many new digital technologies have been introduced in the acquisition of rock drawings: reflectance transformation imaging (RTI) [19; 20], structure from motion (SfM) [24; 31], photogrammetric measurements [21; 22; 28], optical laser scanning (OLS) [24; 32], terrestrial laser scanning (TLS) [15; 27; 31], photogrammetric measurements combined with aerial recordings [12; 16] using an unmanned aerial vehicle (UAV) or combining tachymeter-based tracking of the scanner, stereo and SfM [27]. RTI technology consists in taking approximately 60 photos of the object with a camera placed on a tripod, with changing light directions (evenly distributed on the hemisphere), which, after processing the collected data, leads to the collection of information about the value of the 2.5D model [19]. Other technologies, by using specialised software, allow for the more or less simple building of 3D models of petroglyphs, which significantly facilitates their storage and sharing. Article [22] is noteworthy, as it presents a detailed methodology describing all the stages of creating 3D petroglyph models using photogrammetry.