J.R.R. Tolkien spent decades mapping out Middle-earth on graph paper because everything had to be invented from scratch (and given a name.) Many of his maps weren’t even published until after he died, but today’s fantasy cartographers owe a great debt to his work. They also have a post-modern understanding that to create a believable fantasy map, they have to sow doubt in the minds of readers whether we should trust the mapmakers.
Let me also point out, however, if you’re already a deep map-geek like I am (and I suspect the group of people who read and follow this blog skews pretty strongly in that direction), this program isn’t full of ground-breaking, new information. But, on the other hand, if you’re in that category, you probably haven’t reached your limit on the topic, so I’m guessing you’ll find it interesting, too. It’s less than 20 minutes long.