Found a few things out about the SparseWorld dynmap as I tried to access it and it was not the happiest experience. By default, the spawn is a negative x coordinate, instead of a positive y coordinate, and when manually entering the coordinates, the area is completely black.It's under active development, that's why it's black. I use that as a test server, and I may make it private to prevent that sort of confusion. I think you mean negative Y coordinate, and there's a good reason: In Minecraft, negative Z is north and positive Z is south. I'm working on a demo in the northern hemisphere, where positive UTM coordinates are north, so I just negate the coordinates to prevent the area from occurring upside down.
It'd be cool to see NYC from overhead, just some bug fixes need to occurThe server is now something of a test area for a private project, so I should probably separate it out and make it not publicly-accessible for this portion of the project (while keeping the old SparseWorld Dynmap visible for curious visitors).