The rover needs to be able to autonomously navigate a fixed area. There can be multiple approaches to demarcate the area:

• Use transmitters to demarcate the area and make the rover aware of them to know when it reaches the limits
• Use physical barriers that it recognises when it bumps in to them to demarcate the area (maybe a camera and a specific pattern on the barrier?)
• GPS

The rover needs to be able to stay in it's designated area, and while inside it needs to navigate the area in a way that it will cover all ground in it in a relatively constant pattern. So a regular pattern like this U shaped pattern makes sense:

|     |------|     |
|     |      |     |
|     |      |     |
|     |      |     |
-------      -------

We can also investigate other options. It is worth looking into the possibilities of ArduPilot and Robotics Operating System (ROS)