# Lost on SEIF Slam repeated update landmark

I am working on Sparse Extended Information Slam. I take the reference from Probabilistic Robotics, by Dr.Sebastian Thrun (Chapter 12,page 303). I have some doubt about the implementation of the algorithm. There is a concept of passive landmark and active landmark.

As per the picture at $x_t$ position it sees $y_1$ and $y_2$ and update the matrix as per requirement. Now, lets say that the robot can see landmark $y_1$ again at $x_{t+10}$ position. Then the information matrix $\Omega$ change the $x_t$ vector as $x_{t+10}$ but what happened with the $y_1$ cells row and column?

I cannot figure it out after reading the algorithm several times.

• Please some one clear my doubt. A week passed but don't get any answer. Sep 21 '18 at 2:59