How does Dijkstra's algorithms work inside navfn?

edit

Hi, I have gone through this and this as well . Can someone explain how the global path planner works in details?

EDIT: According to your suggestion, I have visited NavfnROS and navfn. In navfn_ros.cpp, line number 197 , we have makePlan () method defined which calls calcNavFnDijkstra(true) line 285. This calcNavFnDijkstra(true) is defined here, line number 290. It uses

propNavFnDijkstra(std::max(nx*ny/20,nx+ny),atStart);

00302

00303 // path

00304 int len = calcPath(nx*ny/2);

END

I want to remove only Dijkstra's algorithm; I don't want to change the costmap generation, cell updation, obstacle avoidance

I know what is a potential field, but how it is used here; I have no idea. How does gradient line 989 help us in making the global plan? I am using ROS fuerte.