I think the goal is always at the center of the maze (fixed coordinates). This seems to be the case in all the competition videos I've watched. Mouse knows where the center is because size of the maze is known in advance.
for the normal micromouse its always in the center but for the half-sized micromouse it could be anywhere, even the shape could differ and instead of a 16x16 it has a 32x32 grid. if i remember correctly