22 Jan Beneath the Painted Surface
Just as airborne lidar has been able to strip away dense vegetation to reveal thousands of Mayan structures in northern Guatemala, at times the laser scanner can reveal what lies beneath painted structures. Here the newly painted New York State Pavilion from the 1964/65 New York World’s Fair covered years of neglect and graffiti. The intensity feature of the scanning software enables the infrared aspect of the laser scan to uncover earlier paints. How is this accomplished? Our terrestrial laser scanners use a laser in the infrared spectrum and this captures a point cloud representation of a structure. The process also uses visual light photography to capture color data, which is then mapped to the individual points in the point cloud. In the two images presented in the GIF, the color is the point cloud data with the colors affixed from the photography and the grayscale is without the photography and reveals the graffiti as the reflectivity rate of the surface paint and underlying graffiti paint are different.