Extended Kalman filter localisation

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Hey guys, I am doing mobile robot localisation as a project. Now I stuck in obtaining the equations of EKF localisation. My robot moves straight for 10 seconds parallel to x-axis and robot equipped with 2 sonars - in front and in right side. As a landmark I have two lines/obstacles in front of the robot and on the right side parallel to x-axis. Could you please help me to obtain the equations?! The map looks like this:

____________| The robot is in the origin (0, 0), the landmark line parallel to X-axis coordinate is y=-2000mm, the landmark parallel to y-axis is x=4000. I already implemented the motion-based control which returns estimated pose of the robot and covariance matrix. The estimated pose of the robot is given by S=[Sx, Sy, Sth]. What is the matrix form of my observation model Jacobian matrix which is, I quess, is linear. Thanks in advance.