Crowd-sourced mobile phone images for heritage conservation monitoring

We propose quantifying color in crowd-sourced images from mobile phones to monitor built heritage over time. Time-lapse color movies in CIE color space can provide information on a large range of deterioration mechanisms, including soiling, biofilm growth, weathering and vandalism. Citizen science can create large-scale geographical coverage of sites difficult to obtain any other way. We show that the color accuracy of current phones is sufficient for this purpose and demonstrate image registration, color calibration and change detection using mobile phone cameras. For accurate color, a calibration target of known, stable colors need to be in the image field of view.