Since the Island had decided, in its paradoxical wisdom, to rearrange its layout, the Doctor needed to update his mental map of the place. It wasn't an entirely new thing to the time lord, the TARDIS had often felt the need to change room positions or add and remove ones she didn't feel certain regenerations needed. Of course, she was far less attention-seeking in the way she went about it.
Family had come first in the wake of the darkness and he hadn't wanted to be too far away from the Twins or Rose for a while, but since another influx of new arrivals had come, he needed the distraction of the re-mapping to keep the paradox sickness at bay. It was nowhere near as bad as it had been the first year or so he had been on the Island but it still had its flare-ups when a lot of new arrivals turned up at the same time.
His mental map was coming along pretty well, having already reworked the apartments, diner and most major buildings' positions but he could still see and feel some errors. That and he also couldn't help but notice he wasn't the only one out and about at the moment.