Minecraft wiki entry for Development_versions, associated text: Can only be obtained from cartographer villagers.
Used to locate ocean monuments and the new woodland mansions.
Ocean explorer maps are slightly blue, while woodland explorer maps are slightly brown.
Works like a map, but shows the outlines of land and a single structure icon.
Fills in the map with blocks once the player starts exploring the area shown.
When resized, it will still show the structure icon, but will lose the outlines.
When outside the area on the map, the player icon will be smaller the further away the player is.
When 1024 blocks away from the structure, the dot will go from a small icon to a bigger one.