The Library of Congress are using hyperspectral imaging to detect hidden characteristics of their historical map collection, such as colorants, erased inks, hidden overwriting, and fading. The technology aids in authentication and preservation of the works while being non-destructive and non-invasive. This approach has been used to analyse the 1507 Waldseemuller world map, and the L’Enfant plan of Washington, D.C., among other holdings. The technique uses 13 spectral bands from ultraviolet through visible to infrared that can be fine-tuned for precise micro analysis of the maps.
You can read more about the technique and research here. Thanks to my brother, an archivist at LOC, for the tip.
