I think that Simon should have developed/or just has a pretty good sense of orientation, it is so good that gets uncanny, like sometimes it can compete with the eridians one who have the advantage to percibe everything around them and memorize it.
Grace and Rocky, with Simon consent, experiment to see the limitations of this orientation, leaving Simon in differente spots around the biodome, blindfolding him, or changing stuff from places so Simon would be trick by it, but Simon always gets where he wants.
Grace and Rocky has desisted from understanding how this work, but Simon finds the whole thing entretaining so now is a constant effort for the whole scientific crew to find ways to make it harder for him to get to his destination.
Extra:
Sometimes they would just hide Grace and try to see how low takes Simon to find him, the time gets shorter and shorter each time.
