[VikingCoder]

010100110100111101010011

That's binary for the ASCII "SOS" which means Save Our Ship, it's the universal distress code.

It would take you 24 days to send that message. On day one, your first bit is a 0, so you use a black tile. On day two, the second bit is a 1, so you use a white tile.

The satellite imaging system photographs your house and sees alternating tile colors on different days. You try to find the signal of these tiles among the noise of everything else changing in the satellite photo.

It's a completely impractical way to send messages. :(

[hpriebe]

Ah ha! I see.

It might not be practical, but I like the idea of using tech to receive the message rather than send it - in other words, that there might be a way for people on the ground to send a message without tech, since that's something that is inaccessible there.

[VikingCoder]

Satellites also get side-views, not just top-down.

If you wanted to communicate more quickly, you would hang your clothes on a clothesline. Picture black and white sheets.

Day one:

01010011

Day two:

01001111

Day three:

01010011

So, that's 8 times faster.

Or you lay out a bunch of tiles... Tiles are tricky, because if someone asks, "Why are you changing what's on your roof?!" it's hard to answer. Sheets on a clothesline are plausible, though. "I'm doing my laundry!"