The size of the world cannot be reliably deduced from the extent of the data. VWTk assumes a default world size of 500x500. All worlds are assumed to be square. If you know the size of the world you are visualizing you can change it. Currently, VWTk does not store this information, so you have to change it everytime you load data. This will change in a future release.
To change the size of the world, click Tools-->Change world size..., type in a new world size and press enter. VWTk will resize the world and re-layout your data.
