Imaging Changes: Smartphone Cameras and Citizen Science Meet Heritage Conservation

Abstract

Imaging Changes: Smartphone Cameras and Citizen Science Meet Heritage Conservation

Greg Bearman1, Eric Doehne2 and Jon Voss3

1 ANE Image, Pasadena, CA

2 Conservation Sciences, Pasadena, CA

3 History Pin

Cultural heritage is under constant attack from the elements and entropy. The role of conservators is to manage and mitigate change, not stop it. Imaging is a natural tool for measurement and detection, as it it reveals changes in context, unlike point measurement methods. While point methods (FTIR, Raman) can typically provide detailed information on the nature of changes they are not well suited to macroscale and repeated measurements.

We propose a citizen science approach, using mobile phone cameras, to create a fine-grain time-stamped image dataset. This data will serve as inputs for detecting and measuring change and determining rates and patterns of change caused by biodeterioration, material loss, vandalism and soiling. The data also can be used to detect color changes that may be proxies for surface chemical changes such as UV damage, bleaching and pollution-driven chemistry.

The methodology is particularly well suited for built heritage -- historical buildings, monuments, excavated archeological sites and any sort of large-scale cultural heritage exposed to the elements. Accurate color calibration is vital for this program, and we have designed and tested calibration kiosks to be imaged alongside objects. We calibrated mobile cameras against color standards and compared results on minimum detectable color changes with known values of colors on built heritage from biofilms, pollution and other processes.

Crowd-sourcing will enable collection of large numbers of images over time, from remote or urban locations, which would be cost-prohibitive for long-term, mounted site cameras. Using social media, we will create an engagement loop that will make it fun and easy to take images, spread the word and pull in feedback and outreach. “Then and Now” images of popular heritage sites are particularity compelling. Users will use a stand-alone or web based app to frame and take pictures; a translucent overlay will guide users to the correct image and ascertain that all are approximately the same.

Significant computation issues at the back end remain.. The images must be aligned, registered, color-calibrated and corrected for zoom, dolly and other artifacts of acquisition. In addition, we need to adapt existing systems for detecting, quantifying and visualizing change to the needs of heritage sites and develop the necessary ‘glue’ in terms of criteria, design and software for evaluating change. The final output will be time-lapse movies keyed to different changes; these will be cloud based and available to conservators, site manages and the participating public.