Multispectral Analysis Reveals Lost Details on a 16th-Century Portolan Chart

Excerpt from an enhanced version of Bartolomeu Velho’s portolan chart of the east coast of North America, ca. 1560. Compare with the original. Library of Congress.

The Library of Congress reports on how its Preservation Research and Testing Division used multispectral imaging to bring out previously illegible place names on a 16th-century portolan chart of the east coast of North America. Initially the PRTD was brought in to confirm that the chart was legit before the Library purchased it (which it did last fall), but the faded iron gall ink in some areas of the map suggested obscured details that further analysis could draw out and place names that could be made legible again. According to the article, this represents the first time the Library has posted an enhanced image of one of their holdings.