Does Driftscape require an internet connection?

Yes: for Driftscape to work properly, you need internet access (wifi or data). But Driftscape supports viewing through the Save for Offline feature...here's a tutorial video [with steps listed below]: 

On the map, zoom into the area or the POIs you want to save and tap the Save for offline button. Once saved, you will be able to view that content later on when you do not have an internet connection.