Linear 3-D transformations of Landsat 5 TM satellite images for the enhancement of archaeological signatures during the phenological cycle of crops

A linear 3-D transformation that can be used for the enhancement of crop marks to buried archaeological features is developed and presented in this article. The is based on three steps: (1) recalculation of the ground narrowband measurements to the multispectral Landsat 5 Thematic Mapper (TM) sensor, based on the relative response filter of the sensor, (2) application of component analysis (PCA) transformation in order to determine the initial used for the orthogonal transformation, followed by (3) a 3-D rotation of the PCA . The linear coefficients of the transformation were retrieved and adjusted to phenological stages of the crops. The transformation was successfully evaluated both in situ measurements and Landsat 5 TM images in two different case studies. The proposed transformation tends to enhance archaeological better than other established vegetation indices or algorithms, while methodology can be expanded to any other multispectral satellite images using the visible and very near-infrared part of the spectrum.