Creating a Composite Cultural Heritage Artifact - the Digital Object

Advanced digital spectral imaging is now becoming
a key interdisciplinary analytical tool for use in the
examination, assessment and understanding of cultural
heritage preservation and interpretation in the humanities.
This involves the integration of advanced technologies,
work processes and a range of skills from various
fields. This includes experts in materials science and information
technology with social scientists through the
development of methodologies to ensure preservation,
distribution and access to all aspects of cultural heritage.
The critical component of developing this research area
is to develop collaborations between researchers in multiple
disciplines. The Library of Congress is developing
and refining this tool for preservation of significant
cultural heritage artifacts, including the Waldseemüller
1507 World Map, the first and second drafts of the Gettysburg
Address, and the L’Enfant (1791) plan of Washington
D.C. Under the direction of the senior preservation
scientist, Dr. Fenella France, a team of preservation
scientists and imaging specialists developed imaging
and data management capabilities to ensure preservation,
distribution and access to information on these and
other cultural heritage objects. This information proved
critical in supporting collaborations between researchers
in multiple disciplines, enhancing the ability to understand
and mitigate the potential and inevitable loss of
information due to the natural degradation of materials.
Hyperspectral imaging involves the capture of a range
of specific wavelengths in the visible and non-visible
spectrums. To access this wealth of image data, three key
aspects of digital data capture and management must be
addressed:
• The image acquisition process and the required adaptation
for high quality images of large documents
and manuscripts
• Processing of digital images integrated with specific
interpretation for preservation and scholars
• Implementation of effective metadata standards and
data management systems
This paper will primarily address the integration of digital
image acquisition and processing to develop a nondestructive
analytical technique that allows the characterization
of inks, colorants, treatments, substrates,
deterioration, and lost information – all critical elements
for preservation.
Imaging research at the Library of Congress includes the
collection of sequential narrow wavelength bands of images
from the ultraviolet, through the visible spectrum
to the infrared (approximately 300nm – 1100nm). This
hyperspectral imaging collects contiguous wavelengths,
detecting variances in responses from materials in the artifact
at any wavelength or combination of wavelengths.
The team of preservation and imaging scientists working
with a MegaVision 39 Megapixel monochrome camera
and Equipoise LED EurekaLights image the items of
cultural heritage – documents, leaves of manuscripts,
daguerreotypes, in each spectral band. This yields a
large data cube of digital images and metadata for each
artifact. The resulting collected images are digitally
combined with or subtracted from each other to form the
processed image or “digital object” that provides greater
analysis and interpretation of the original real cultural
artifact. These processed images contain a wealth of information,
but it is the significant levels of multidisciplinary
interpretation required to process and analyze the
data collected, that forms the new digital object.
The Library of Congress is building on the past two
decades of characterization of ancient texts and documents
using advanced digital imaging techniques. It is
developing these research methods to advance studies of
other media and cultural heritage items, as well as new
techniques for specific preservation requirements. The
ongoing research and development highlights the utility
of transferring advanced imaging techniques developed
for defense and astronomical studies to the preservation
of significant cultural heritage artifacts. Specific
studies that have led to the current developments in advanced
digital imaging include the Dead Sea Scrolls,
the Khaboris Codex, Archimedes Palimpsest, and the
Oxyrhynchus Papyri. Each of these studies has revealed
some of the issues and challenges involved with applying advanced imaging and processing techniques to researching
cultural heritage documents and artifacts. For
example, complex image processing previously used to
recover images from astronomical telescopes, has been
adapted to reveal what the original woodblock that was
used in the printing of the Waldseemüller map probably
resembled. Integrating an analysis of the techniques
used by a woodcut maker in the 1500s informs understanding
of materials and choices made even though the
original woodcut no longer exists. All of this research
underscores the need to integrate social and material sciences
with the digital object to better understand issues
of technological and other choices in the creation of the
original object. Styles and the delicate detail attained
were compared with copper engraving by researchers in
the 20th century still attempting to understand the innate
technical skills. Layering the information to show later
additions by cartographers and printers adds more to the
complexity and potential utilization of the digital object.
The ability to process this information needed to collect
useful data associated with substrates and media without
physical sampling is critical to the assessment and preservation
of many international items of cultural heritage.
In addition, analysis for transcription and translation of
deteriorated ancient texts requires collaboration between
conservation and scholars for effective translation. These
aspects will be outlined in more detail in the paper.
While advances in image acquisition processes are critical,
it is the post-capture processing that creates the new
digital object of interest in this discussion. This processing
and interpretation of acquired images is integral to
the creation of the information necessary for the preservation,
analysis and assessment of these cultural artifacts
through digital spectral imaging. This digital image processing
has evolved from simply choosing the best spectral
band and collecting images in that band (mono-spectral),
through principle component analysis of specific
wavelength combinations and pseudo-color processing,
to the current advanced algorithmic image processing
utilizing the combination of registered images in various
non-visible and visible spectrum regions.
As noted previously, hyperspectral imaging creates large
volumes of data for processing, analysis and interpretation
and requires understanding of these new digital
objects and the levels of information contained within.
Data and metadata management is imperative to integrating
digital imaging and processing capabilities for
studies of cultural artifacts in the humanities. Creating
the digital object requires effective systems and information
management to ensure that the large amounts of
digital data generated can be readily acquired, stored,
archived, accessed, processed and linked to other data.
The creation of a new “digital object” that combines the
real cultural artifact and the processed digital files and
information has established a new category of cultural
artifact in the humanities. The resulting composite digital
object allows insights into methods of construction,
the impact of society and technology and scholarly information
on how this informs researchers and our understanding
of previous societies. This can be used to
address questions such as:
• Why did artists and artisans develop and employ
those specific techniques that were used to create
the real artifact?
• How were these restricted or informed by available
tools, cultural norms, religious or moral beliefs?
• Did the creator demonstrate a break from tradition
that was only now being revealed through the availability
of advanced spectral information?
Integration of information from the original object and
the digital imaging is a critical component in the organization
and access to the digital object. Developed from
GIS, the concept of “scriptospatial” or "image-spatial"
tagging of key points on the images is the equivalent
of a global positioning system for documents and objects.
The linkage of information from other scientific
analyses, or scholarly interpretations of revealed details
revealed by the advanced digital image processing is an
important element in the generation of an integrated digital
object that allows the interpretation and assimilation
of a range of data that is at times in different data sets.
The critical breakthrough in the adoption of hyperspectral
digital imaging was the maturity its development
– resolution, integrated conservation safe lighting and
management – to concentrate on and answer these questions,
while also addressing the issues involved for this
technique to become accepted as a true non-invasive
non-destructive analytical tool with no risk to fragile
historic artifacts in the field of cultural conservation.
Hyperspectral imaging has the capacity to reveal information,
data and details not visible or accessible from
the historic artifact itself due to deterioration. This highlights
the necessary integration between materials science,
digital spectral imaging and the social implications
of retrieving lost information. This generation of new
information includes that created from advanced digital
image processing of the large volume of acquired data.
In conclusion, providing useful information to support
conservation research and scholarly studies requires the
effective integration and application of new technologies, work processes and technical skills to the field. The use
of multi- and now hyperspectral imaging as an effective
conservation tool has allowed the development of nondestructive
analytical tools that allow the safe analysis
and examination of texts and documents. This requires
the integrtion of a range of associated activities and processes:
imaging artifacts in a range of spectral bands,
capturing important metadata about the digital records,
storing the digital data and associated metadata, processing
the images and data to yield useful information, and
making the information available for researchers in the
humanities, conservation professionals and the public.
Future accomplishments in the creation of a new digital
object will be dependent on economic development
of integrated image information systems, continued advances
in image technology, and the effective integration
of data access, storage, management and interpretation.
This requires continuing innovation and collaborations
of imaging and preservation scientists, information technology
professionals, conservators and researchers in the
humanities.
References
Casini, A, et al. Image Spectroscopy Mapping Technique
for Noninvasive Analysis of Paintings, Studies in Conservation
44 (1999) 39-48
Easton, R.L. Jr., Knox. K, Christens-Barry, W.A. Multispectral
imaging of the Archimedes palimpsest. In: Proceedings
of 32nd Applied Imagery Pattern Recognition
Workshop (IEEE-AIPR’03) (2003) 111–116
France, F.G. Managing digital image repositories as key
tools in the preservation of cultural objects, Imaging Science
and Technology Conference, Arlington, VA, 2007
France, F.G. and Toth, M.B. Developing cultural heritage
preservation databases based on Dublin Core data
elements, Dublin Core Conference, Manzanillo, Mexico,
October 2006
Grenacher, F. The Woodcut Map: A form-cutter of maps
wanders through Europe in the first quarter of the sixteenth
century, Imago Mundi, Vol 24 (1970) 31-41
Knox, K. “Enhancement of overwritten text in the Archimedes
Palimpsest,’’ in Computer Image Analysis in
the Study of Art, San Jose, California, Proc. SPIE, vol.
6810 (2007)
Knox, K.T. et al., “Image Restoration of Damaged or
Erased Manuscripts”, European Signal Processing Conference,
Lausanne (2008)
Knox, K. and Easton, R.L. Jr.: Recovery of lost writings
on historical manuscripts with ultraviolet illumination.
In: Fifth International Symposium on Multispectral Colour
Science (Part of PICS 2003 Conference), Rochester,
NY (2003) 301–306
Plaza, A, et al., Recent Advances in Techniques for Hyperspectral
Image Processing, Remote Sensing of Environment,
Elsevier Science, July 2007
Reedy, C. L. and Reedy, T. J. Relating visual and technological
style in Tibetan sculpture analysis, World Archaeology
25(3) (1994) 304-320
Toth, M.B. “Management of Digital Archives for Integrated
Web Access to Scientific and Cultural Information”,
Society for Imaging Science and Technology,
Archiving Conference, Arlington, Virginia, May 21-24
(2007)
Toth, M.B., Emery, D. “Encoding Archimedes Work
with TEI to Complete a 10-Year Program”, Text Encoding
Initiative Annual Members Meeting, London (2008)
Walvoord, D, Easton, R. Jr., “Digital Transcription of
the Archimedes Palimpsest”, IEEE Signal Processing
Magazine p. 100-104, July (2008)