This paper is part of the 2017 3D Digital Documentation Summit.

Scientific photogrammetric imaging of a large-scale Diego Rivera fresco mural

This paper will share our experience capturing the fine surface details of a 6.7 by 22.5 meters (~ 151 square meters) 1940 fresco by Diego Rivera.

The project had multiple motivations: to produce benchmark historic documentation of the current state of the mural; provide details of the mural’s surface for conservation and restoration planning; promote awareness and research of the mural iconography and the brushwork of the artist.

In 1940, Mexican artist Diego Rivera (1886-1957) painted a huge mural (22 feet x 74 feet), an inspiring vision of the unity of art, religion, history, politics, and technology in the Americas. Originally titled The Marriage of the Artistic Expression of the North and of the South on this Continent, it is commonly known as Pan American Unity. Rivera created the work during the 1940 season of the Golden Gate International Exposition (GGIE) at Treasure Island on the Bay in San Francisco, California. The mural was the centerpiece of a program called “Art In Action” that featured many artists creating their works while the public watched.
Several aspects of the project will be highlighted including: the determination and achievement of the resolution and precision requirements; the metadata strategy for the imaging data; and considerations for viable outputs for the web and other distribution channels.

Because the fresco surface is so subtle, a high-resolution (sub-millimeter) capture was required. Approximately1500 overlapping 50MP images were collected following a rule-based, data acquisition error minimization and software independent capture methodology.

Another key goal of the work was to acquire appropriate metadata about the imaging project to aide in data reuse and scholarship. We employed a novel metadata acquisition and management approach using software tools developed by Cultural Heritage Imaging in collaboration with the Centre for Cultural Informatics of the Foundation for Research and Technology Hellas in Heraklion Crete.

The methodology and tools are designed for digital representations that are built with computational photography technologies, and that are intended for use in interdisciplinary science and humanities scholarship. The software builds a “Digital Lab Notebook” and takes the form of a user-friendly toolkit, which makes it possible to document not only the algorithmic transformation of photographic data, but also the context in which the photographs were created. Current computational photography technologies are based on the algorithmic extraction of information from multiple photographs, generating new information not found in any single photo. This software’s new metadata and knowledge management methodology produces metadata-rich empirical digital data. In turn this managed metadata enhances the likelihood of the information’s sustainability.

The result is CIDOC Conceptual Reference Model (CRM) mapped Linked Open Data (LOD) describing the capture context and data validity. The tools use a natural language interface to collect relevant information about the subject, people, project, and equipment. The user needs no CRM or LOD experience to produce this rich metadata result.

With a sound metadata foundation, the advanced photogrammetric imaging data collected for this project will assure a reliable baseline of the mural’s current condition. It will also ensure the reusability of the data for future generations.

Author Biographies
Carla Schroer is co-founder and Director of Cultural Heritage Imaging (CHI), a nonprofit corporation dedicated to advancing the state of the art in digital capture and documentation of the world’s cultural, historic, and artistic treasures. Carla leads the training and software development programs, while also working on field documentation projects using Reflectance Transformation Imaging and photogrammetry. She spent 20 years in the commercial software industry directing a range of projects including Sun Microsystems’ Java technology.

Mark Mudge is co-founder and President CHI. He has worked as a professional bronze sculptor and has been involved in photography and 3D imaging for over 25 years. He is a co-inventor, with Tom Malzbender, of the computational photography technique, Highlight Reflectance Transformation Imaging. He has published twelve articles and book chapters related to cultural heritage imaging and serves on several international committees, including the International Council of Museums’ (ICOM) Documentation Committee (CIDOC).

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