Hacker News Reader

Comment by draz | Hacker News Reader

out of curiousity -- could the Manhattan grid be naturally used for satellite calibration (thus masking intention)? Could we install objects on top of buildings to help calibration (surreptitiously)?

View on HN

Theoretically, maybe, but it's not very practical. You need to have very good ground truth (i.e. know exactly how wide that street is) and the spacecraft needs to be directly above Manhattan, otherwise tall buildings will obscure your calibration target.

FWIW, I was on a calibration support team for the recently launched NPP satellite. The engineers and scientists go to great lengths to perform calibration and characterization before launch. Common calibration targets after launch: deep space, the moon, polar ice caps. Things we know a great deal about, have a clear view to, and don't change much.

If a city grid was sufficient, why would China need to build massive structures in the desert? They've no shortage of city grids. Come to think of it, they've no shortage of massive development projects either. If a city grid worked as a surreptitious calibrating tool, surely they could work the design into a factory system, evap pool project or university campus. (I think an actual city would be out of the question due traffic concerns)

The first thing that comes to mind here is the enormous red bullseyes that Target puts on top of all of its stores. They're visisble from airplanes and satellites, but their symmetry would make them less useful for calibration.

An example: http://craphound.com/images/googleeasrthad.jpg

That's a brilliant move on Target's part-- how easy must it be to find your nearest target on Google/Bing/Etc Maps? Pretty forward thinking of them, if you ask me...

Reply on news.ycombinator.com