GPS

Following my bike route on Google Earth yesterday, I was amazed to find that the data was accurate enough to show that I cycled out on one side of the road and back on the other.

That, and the importance of GPS evidence in the unfolding UK/Iran dispute, sent me to Wikipedia to ferret out more details of the Global Positioning System.

It is technically and historically fascinating stuff . Look at the section on Selective Availability for example. The paragraph that struck me the most however was:

The satellite constellation is managed by the United States Air Force 50th Space Wing. The cost of maintaining the system is approximately US$750 million per year, including the replacement of aging satellites, and research and development. Despite this fact, GPS is free for civilian use as a public good.

The ability to for ships, cars, emergencies and even joggers and cyclists precisely to identify their locations must be an enormous economic and social boon to the world.

Providing the underlying infrastructure free of charge is a noble deed, so I'd just like to say thank you very much to the USA.