Cost maps for Navigation

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I have two questions in mind. question 1 : As laser range finder will give partial view of the environment; how to generate the entire map of the environment which I think will serve as a global cost map in YAML format.

question 2: Can a map of such kind be augmented with the start position coordinate (x,y) and goal position coordinate (x1,y1). Can I track the robot (x,y) coordinate in terms of the Global cost map (or local cost map) at any point of time.?

Again in navigation tutorial, it is mentioned that the navigation stack doesn't need map to operate.