 This article uses the word 'GeoWall' as a convenient trisyllabic equivalent for "low-cost polarization-based dual-projector interactive 3D stereoscopic system".Interactivity is a crucial aspect to GeoWalls, particularly for real-time data exploration.Without interactivity, a GeoWall is merely a system for viewing 3D films – a cheap 3D IMAX on a smaller screen.