Google seems to attack this problem from a variety of expensive angles [1], [2]. But in the end, the simplest thing sounds best to me [3].

[1] http://glassbox-design.com/2009/google-goes-aquatic-photos-i...

[2] http://www.engadget.com/2010/06/17/another-reason-to-want-a-...

[3] http://www.reddit.com/r/pics/comments/6ceia/google_naps_phot...