NDLI: Measuring changes in cultural heritage objects with Reflectance Transformation Imaging

Content Provider	IEEE Xplore Digital Library
Author	Manfredi, M. Williamson, G. Kronkright, D. Doehne, E. Jacobs, M. Marengo, E. Bearman, G.
Copyright Year	2013
Description	Author affiliation: Georgia O'Keeffe Museum, Santa Fe, NM, USA (Kronkright, D.) \|\| ANE Image, Pasadena, CA, USA (Bearman, G.) \|\| New Mexico Highland Univ., Las Vegas, NM, USA (Williamson, G.; Jacobs, M.) \|\| Conservation Sci., Pasadena, CA, USA (Doehne, E.) \|\| Univ. of Eastern Piedmont, Alessandria, Italy (Manfredi, M.; Marengo, E.)
Abstract	Sites and objects of cultural heritage - from art to ancient inscriptions to ruins - are under constant attack by time and the environment. While much is known about how material components change from laboratory-based artificial aging, very little is known about the process or rates of change of actual objects and sites in situ. Reflectance Transformation Imaging (RTI) is a quantitative method that captures surface normals. In our case, it provides detailed information on the geometry of the object surface. We show that RTI can be quantified for use as a method for measuring change in cultural heritage objects. The past decade has seen the rapid evolution and application of computational photography methods to document important works of human heritage, from art and architecture to archives and archaeology. The next logical step involves defining just how reproducible and precise these methods can be to use them to measure rates of change for important works of cultural heritage. The need is to move to calibrated, quantitative image datasets for reproducible imaging. We measure the precision of computed surface normals , which define the basic repeatability of RTI. Our results show that the average included solid angle for RTI sensitivity fitted to the Hemispherical Harmonics (HSH) polynomial function is 0.003 steradians (3 sigma), while the older Polynomial texture map (PTM) method is much less sensitive (0.5 steradians). The absolute sensitivity of the method is the minimum variation of the normal that can be statistically considered a change of the object. It is calculated considering the average value of the normal of each single pixel. The solid angle of the cone of variation represents the statistical limit (3 *σ). Analysis of multiple RTI data sets from objects that have changed between image capture sessions results in a map of change that can easily be evaluated by conservators.
Sponsorship	IEEE France Sect.
Starting Page	189
Ending Page	192
File Size	1755400
Page Count	4
File Format	PDF
ISBN	9781479931682
e-ISBN	9781479931705
DOI	10.1109/DigitalHeritage.2013.6743730
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2013-10-28
Publisher Place	France
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Measuring damage Sea surface Normals Surface morphology RTI Reflectance Transform Imaging PTM Cultural differences Sensitivity Cultural Heritage Imaging Rephotography Polynomials Polynomial Texture Mapping Monitoring
Content Type	Text
Resource Type	Article

Sl.	Authority	Responsibilities	Communication Details
1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
5	Website/Portal (Helpdesk)	Queries regarding NDLI and its services	support@ndl.gov.in
6	Contents and Copyright Issues	Queries related to content curation and copyright issues	content@ndl.gov.in
7	National Digital Library of India Club (NDLI Club)	Queries related to NDLI Club formation, support, user awareness program, seminar/symposium, collaboration, social media, promotion, and outreach	clubsupport@ndl.gov.in
8	Digital Preservation Centre (DPC)	Assistance with digitizing and archiving copyright-free printed books	dpc@ndl.gov.in
9	IDR Setup or Support	Queries related to establishment and support of Institutional Digital Repository (IDR) and IDR workshops	idr@ndl.gov.in

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