I think it's definitely military or government based. You can see several different things: http://maps.google.com/maps?saddr=4...274658&vpsrc=0&mra=mift&mrsp=0&sz=13&t=h&z=13 If you drag right, you can see another grid with no outer border.
During the fall of 1941, prior to Dec 7th, if you would have flown over Japan imperial palace (or used satellites to take a picture), you would have seen a huge pond laid out just like Pearl Harbor, in full detail, etc. ....if this is Washington, DC very interesting. (but I have looked at the DC map and cannot match it up)
I forget where I saw it but some NASA scientist speculated that these were calibration patterns for spy satellites, but that given the size and width of the lines, the satellites are not very strong.
