Astral map

The Doctor owned in his first incarnation an astral map which recorded the astronomical locations of various stars and planets. Upon arriving on Vortis, the Animus forced the Doctor to use the map to discover the plans of the invading Menoptera. (TV: The Web Planet)

The First Doctor used the map again when the Drahvins allowed he and Steven Taylor to go back to the TARDIS to find out how many days before the planet they were on exploded. The Doctor discovered it was not a fortnight, but merely two days before it exploded. (TV: Galaxy 4)