From a story in Yale News:
A team of researchers and imaging specialists at Yale University is recovering faded and hidden (invisible to the eye) information from a 1491 map using multispectral imaging technology. Their work is yielding new discoveries about how the world was viewed over 500 years ago, and supports the view that African sources were important in its creation:
The way Martellus depicted Africa was actually based on African sources. According to Cummings, the way Africa is drawn on the map actually came from Ethiopian sources — specifically, “three Ethiopian delegates to the Council of Florence in 1441.” The council was called by the Pope — who invited the Ethiopian delegates, providing insight into how the African continent was shaped.