Photogrammetric analysis of a heritage ceiling

Conservation of the painted ceiling at the historic Hampton Court Palace requires the condition of the ceiling to be monitored for signs of formation of cracks and flakes in the surface. Miniature monochrome cameras and LED lights were mounted on a horizontal bar, and raised by a telescopic mast to 60 cm below the ceiling. Images from the cameras were captured simultaneously by purposedeveloped software in a laptop computer at floor level. A series of image pairs was acquired at each location, rotating the mast between each pair. Images were enhanced in local contrast by a modified Wallis filter. From the image set a dense and accurate point cloud was generated, using a photogrammetric bundle adjustment procedure, from which 3D surface details could be visualised.