Наскальные изображения Гачуурта (Монголия): новые наблюдения
The article deals with the results of contactless three-dimensional documentation performed in the Mongolian rock art site Gachuurt (“Gachurtyn amni hadny zurag”). Paintings of Gachuurt are of a peculiar kind, typical for a relatively small area, covering the taiga-steppe mountainous terrains of Central and Eastern Mongolia and southern Buryatia. A specific feature of such paintings in red are the images of “fences” filled with rows of dots, accompanied by drawings of people, animals, birds and the road symbol in the form of two parallel lines. Similar rock art paintings are dated back to the second half of the II-I millennia BC. Patinization, surface hue changing and the pigment lead to the low visibility of the image shapes, resulted in the provoked tracing of images for sketching and photographing. Modern non-contact documentation is performed by digital photography with subsequent photogrammetric processing of images and the development of three-dimensional polygonal models. The photographic texture of the models was subjected to a number of transformations that improved the clarity of the raster image and allowed to perform three-dimensional vectorization of the drawings. The results of vectorization were compared with the drawings carried out by traditional methods (eye-sighted sketching, tracing, including the use of contouring of the rock paintings with chalk and graphite pencil), while some paintings not included in the published sketches were revealed. The analysis of the collected data allows drawing a conclusion about the continuing degradation of drawings under the influence of natural factors (temperature fluctuations, wind corrasion) and human impact on the monument. Comparison of the results of vectorization with the sketches of previous years shows that some of the drawings have already been ruined as a result of the collapse of the rock, and the remaining drawings are under threat of destruction and may be lost in the coming years.