measurements and that means measures in all four directions and it checks whether it's a wall or not in each of those directions it's a noisy sensor and we're going to not go through the math here we're going to qualitative let's see what happens well if it's if it's really over there but we of course don't know where it is the gray e the uniform gray means our distribution is uniform over all possible locations we show the location of the robot just to you know know what's going on but the robot doesn't know that robot just could be