The ellipses represent the uncertainty of the landmark and the robot
Even if the robot does not move, the uncertainty increase due to the noise in the motion model
When the car passes by a landmark for the first time, it passes on its uncertainty to the landmark
If the car passes by a landmark for the second time, the uncertainty of the car is reduced due to
measurement. Coming back to the same landmark has helped the car to reduce the uncertainty in its own
position
If a car is not moving, but a landmark is within its field of view, the car's uncertainty will not
increase much