Photosynth, the tech demo that trawls image sharing websites for geographically tagged photos and then pieces them together to form pseudo 3D models of popular tourist destinations, is stitching an increasingly coherent spatial simulation.

However, the edges of the scenes in these demos have always made me curious about the unmapped portions of the 3D model. While there is an abundance of data for the frontal elevations of Notre Dame or Piazza San Marco, but what of the periphery of these buildings? The parts of the building less likely to attract the attention of hungry tourists? And then what about the laneway around the corner? Or the street two blocks to the south? There may be a handfull of photographs that describe parts of these areas, but likely not enough to piece together a rich 3D model.” (Super Colossal)