Why does Mark have to move to the Schiaparelli crater in The Martian?

In the science fiction novel The Martian by Andy Weir, astronaut Mark Watney is left behind on Mars, when he is presumed dead in an intense storm. He has to learn to survive on the hostile planet with limited resources. In each case that he comes up against obstacles, he keeps working until he finds solutions to the problems he encounters. For instance, in handling the issue of having enough food to survive, he learns to grow potatoes in the habitat. To communicate with NASA, he salvages technology from past Martian missions.
The journey to Shiaparelli crater is part of his long-term survival plans. He wants to not only survive but also eventually get off Mars. To make this happen, he plans to travel 3,200 kilometers to Shiaparelli crater, which is the site where the next Martian mission will land in four years and where a MAV is already positioned for them. He modifies a rover to be able to make the trip. Eventually, he manages to reach Shiaparelli crater, but the Hermes, the spacecraft with his original crew, comes back for him. He uses the MAV to get far enough into space so that the Hermes crew can intercept and save him.