New Applications of the Image Grand Tour

The image grand tour (IGT) is a method for visualizing multispectral images or multiple registered images. Such images can be described as having a multivariate pixel vector associated with each pixel. Examples are the RGB values of a photograph or the multiple spectral and infrared readings from remote sensing satellites. The image grand tour projects a linear combination of the pixel vectors into one-dimensional space (for each pixel) and then renders these projected values as a gray-scale image. An animation of the projected images is obtained by using different linear combinations of the pixel vectors. While the image grand tour was initially used to highlight mines in a minefield, this paper presents new applications of the image grand tour. We use the IGT to find hidden rock art in photographs from sites in state parks in Texas and to reveal features in satellite imagery from the Multi-angle Imaging SpectroRadiometer (MISR), one of the instruments aboard NASA's Earth Observing System satellite Terra.