Viewpoint invariant image retrieval for context in urban environments

We outline work in progress towards a scalable system capable of quickly identifying buildings and other outdoor urban structures from photographs. Salient characteristics of the skyline are extracted and correlated using a minimal edit distance metric to identify a subset of potential matches in a database. This subset is then refined using a slower but more precise affine invariant feature comparison to identify the best match. Our system is envisaged as an alternative to GPS where users may not have access to expensive GPS equipment or a reliable GPS fix, or orientation may be a complicating factor (for example, several landmarks present at a single location).