Capturing Similarities in Rock Art

Photo: Eamonn Keogh sits next to rock art

NGS/Waitt grantee Eamon Keogh collecting data at the Pu'u Loa petroglyph site close to the Kilauea volcano in Hawaii.

Image courtesy of Eamonn Keogh

About the Project

NGS/Waitt grantee Eamonn J. Keogh and his team are attempting to digitally archive images of rock art, or petroglyphs, found in the Southwest United States and making these available to the public.

Image: An abstract and animal petrogypgh

An abstract (top) and animal petroglyph (bottom) which has been traced and issued as queries to the database that NGS/Waitt grantee Eamon Keogh and his team are building. The list of the five nearest matches to each are shown left to right.

Image courtesy of Eamonn Keogh

Petroglyphs are images created by removing part of a rock surface by incising, pecking, carving, and abrading. Petroglyphs are one of the earliest expressions of abstract thinking and are considered a hallmark of humanity. Beyond their value as an aesthetic expression, petroglyphs provide a rich body of information on several different dimensions. Motifs can, at least in theory, be identified and traced through time and space, which in turn may shed light on the dynamic histories of human populations, the patterns of their migrations and interactions, and even continuities with present indigenous societies.

Studies of rock art have implications beyond anthropology and history. For example, a recent study postulates the existence of a now-extinct Australian bat species based on extraordinarily detailed pictographs known to be at least 17,500 years old. Petroglyphs have been used in studies of climate change, and the changing inventories of species in the Dampier Archipelago from the Pleistocene to the early Holocene periods have been reconstructed partly using petroglyph evidence. However, in spite of these successes, progress in petroglyph research has been frustratingly slow.

Image: Image: Clustering of Southwestern USA rock art

Clustering of Southwestern USA rock art

Image courtesy of Eamonn Keogh

This could be because the extraordinarily diverse and complex structure of rock art images defies most existing image matching algorithms. Most approaches are simply not suitable for capturing the similarity of petroglyphs, and those that are, even in limited cases. In this work the team will introduce a novel distance measure for rock art, showing that it can correctly capture the subjective (and where available, objective) similarity between petroglyphs. They hope to show how they can use this distance measure as a basis for several higher-level “data-mining” algorithms (e.g., finding repeated motifs, clustering, or simply enabling query-by-content).

In this work Keogh and his team will identify the reasons for this, and introduce a novel distance measure and algorithms, both of which allow efficient and effective data mining of large collections of rock art.

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