## 1 Introduction  
Petroglyphs, the rock drawings carved by representatives of different cultures throughout human history, are usually the work of people of the era before the creation of alphabets and inscriptions. They are a pre-literary form of presenting stories and ideas, in use from around the 10 th millennium BC to almost modern times. Petroglyphs are found on all continents of the world except Antarctica, the continent considered uninhabited by humans. These drawings are perhaps the oldest evidence of human civilization and intelligence. Their exploration, documentation, and preservation for future generations is a very important element of protecting the cultural heritage (CH) of mankind.  
Petroglyphs, as human rock art, occur mostly in currently little-known and not very frequented places, i.e., caves, mountain gorges, sea cliffs, rocks in desolate places, etc. Such places are usually not protected, and the nature of petroglyphs--rock drawings, does not allow them to be moved to safer places without irreversible damage to their surroundings. Petroglyphs are therefore exposed to various threats, leading to their loss for humanity, and also as a result of human activities.  
The theft of rocks with petroglyphs occurs in practically all countries on all continents. For example, in California, USA, petroglyphs [1] made by the local Paiutte tribe and held sacred by them, were stolen by cutting the stones they were carved on (Figure 1). A similar case took place in Nevada, USA [2] and Tasmania [3]. There are also reports of petroglyphs being treated as souvenirs by tourists [4]. In addition to stealing, acts of sheer vandalism against petroglyphs are noted. For example, vandals have irrevocably damaged petroglyphs in Arizona, USA [5] and Kyrgyzstan [6]. These are just examples of the destruction of petroglyphs, and there are more such cases all over the world.  
Unfortunately, there are also errors of petroglyph conservators [7], leading to the partial destruction of monuments during restoration works. This leads to the need to remove incorrectly selected protective layers, which is not always possible, and always carries the risk of further damage to the monument. A description of the method of removing aged acrylic coatings (also used for the maintenance of petroglyphs) from wall paintings with the use of microemulsions, can be found in [8].  
Such cases occur all over the world, and therefore urgent and permanent documentation of petroglyphs that have survived to this day should be a priority. This is made possible by the digital technology which consists of 3D scanning of their geometry, appearance and position. The ever more popular and affordable tool that could be used for this are 3D terrestrial laser scanners (TLS).  
The purpose of this work includes:  
1. Adaptation of the 3 DScaMITE [9] methodology, developed for scanning cultural heritage objects with 3D TLS, to the scanning of petroglyphs in the places of their occurrence.
2. Verification of the proposed adaptation during the scanning of petroglyphs at The Petroglyphs of Cholpon-Ata Museum in Kyrgyzstan.
3. Verification of the usefulness of the obtained data to confirm or reject the thesis about improper conservation of petroglyphs.  
The remaining part of the paper is organised as follows:  
* Section 2 provides an overview of publications on documenting rock art and the methods of its protection;
* Section 3 discusses the main aspects of 3D TLS scanning, and presents modifications to the 3 DScaMITE methodology for petroglyph scanning tasks;
* Section 4 discusses the effects of scanning petroglyphs at Cholpon-Ata and discusses the results in terms of confirming the thesis about the improper conservation of petroglyphs.  
Figure 1: An example of a wanted poster for petroglyph theft [1].