# Hyperspectral Imaging Techniques for the Study, Conservation and Management of Rock Art
## 1 Introduction  
Prehistoric art is an extraordinary manifestation that documents, with great detail and precision, some facts and animal species that coexisted with the humans of Paleolithic times. It is the first industrial and technical heritage of history, and such a singular phenomenon must be protected [1]. It was made by making incisions and/or applying natural pigments mixed with water or organic elements on a rock surface, which for millennia has been subjected to different factors of natural and anthropogenic alteration that may have caused its deterioration or disappearance.  
The deteriorating factors can act in an isolated or combined way on this cultural heritage and its support, and include dirt, impacts, flaking, disintegration, washing, glazes, coatings, etc.  
The conservation of industrial, technical and cultural heritage requires a deep understanding of the significance and complexity of a place. Good conservation of our heritage is based on informed decisions, and good documentation ensures that knowledge of heritage places will be passed on to future generations.  
This work analyses, develops and implements a methodology to generate information not visible to the naked eye due to dirt, washing, glazes and coatings. This information not only improves the visualization of the panels, but also helps us to understand how they were created and sheds light on the stratigraphy or sequence of the execution of different motifs.  
The methodology is applicable to any rock art panels, and any cultural or industrial heritage objects in general, that need to be studied or controlled in time. The method has been tested on a panel that has been studied since the beginning of the 20 th century, which presents a series of complex cases to solve such as superposition of paints, calcite glazes, pigment-sketch combination, etc.  
Traditional rock art documentation systems are subjective [2], as an individual decides, usually by direct visualization, whether a unit is part of the panel or not. Throughout history, harmful methods such as casts and direct molds have been used, as well as others such as analogue, digital, ultraviolet and infrared photography, which have contributed to create \"digital tracings\" from images processed using image software. In all of them, it is an operator who decides whether or not the panel belongs to the class. Such subjectivity must be avoided, and hyperspectral remote sensing is an optimal tool for this.  
A plethora of techniques, analyses and applications for hyperspectral remote sensing have been developed in the last few decades [3]. It has been used for the documentation of murals [4], detection of buried archaeological relics [5], and exploration of their geologic [6] or mineralogic composition. It has a number of advantages [7]: It is considered a safe detection technique because it is non-contact and non-destructive. Another advantage is its high spectral resolution with multiple bands and narrow bandwidth, i.e., it allows a continuous spectral response to be obtained for each pixel of the image. Because of these unique features, hyperspectral images have been used in conservation [8] and the study of artefacts [9] and to reveal hidden details in ancient manuscripts and paintings, although its use in rock art [10], and in cultural and industrial heritage objects [11], has been scarce and relatively recent.  
The main objective of this study is to propose a method of generating the cartography of pigments and improving the visualization of aspects of rock art not visible to the naked eye due to the causes previously mentioned, as well as to understand its process of creation or the sequence of execution of different motifs.