When preparing a map for yourself as a writer or even more so as a GM, it is a good idea to only detail it as much as you really need to in order to get started, so you allow yourself as much freedom as possible to define in more detail as best fits the progression of your story/game later. (It is more important for a GM, since a writer can go back and change the map during writing if need be, whereas a GM probably has committed to his players basic facts of geography by the time he may regret them later.) Also, spending a lot of time on the map at this point tends to take out time that should be spent on writing/adventure prep. This is definitely enough to get started with.