This map of when cities pass the 1 million population barrier, 1775 – 1975 is a demonstration of temporal GIS features currently under development in worldKit.
GIS usually computes along the spatial dimension. Yet many processes and systems investigated with GIS have a significant temporal dimension: urban planning and land use, hydrology, fires, ecological change.
Methods of interaction and presentation in Temporal GIS are still open questions. I’m really curious to see how this works out.