[akira2501]

Neither. It's just such a habit to type miles. I meant 510 trillion square _meters_, which google and wolfram alpha tell me is correct.

In any case.. the reason I chose that is because that's probably close to a reasonable maximum single pixel resolution for tracking imagery. I wanted the scope of the problem to be obvious by choice of units; unfortunately, I screwed that part up. :(

[david-given]

Been there, done that, bought the aardvark. I mean T-shirt.

(And, of course, it didn't occur to me that 1e6 million square metres is a square kilometre...)