It's another birthday of sorts. On 3rd of May 2000, the first GPS-driven geocache was left in the wilds outside of Seattle by Dave Ulmer. It was found a couple of days by someone else later because the GPS-coords had been posted on a usenet board - what passed for "social media" at the turn of the century. Geocaching is surely A Good Thing - it gets folk out in the open air; it requires them to use their powers of observation and to limber up the ould brain-cells. The fact that many children play the game with or without their parents is a potential antidote to obesity. Of course, I'd be all for it because I love treasure-hunts, and have put one together almost every Easter over the last 30 years, ever since The Boy was old enough to run in the woods alone.
But geocaching is just a techie extension of the far older hobby of letterboxing. In May 2000 you were able to post useful 12-figure accurate identification of locations because President Clinton had just signed an ordinance which denobbled the signal from the US military's GPS satellites. The nobbling theretofore was called "selective availability" which added random noise to the true coordinates so that Russkies or Terrists couldn't accurately point their nukes at US targets. As the noise amounted about 50m off, that didn't seem to make a lot of differ on the dirty-bomb targetting front. And, because there was a market and because it was a techie-challenge, you could buy a pretty effective solution to eliminating the SA noise so that Joe Public knew where he was. There is no point in having a system in place that annoys and discommodes your own citizenry while forming no impediment on The (Fur) Blackhats. Geocaching grew and grew but I suspect that the intellectual challenge is a little less than finding the treasure a la mode de Gold Bug. Wot? Haven't read the Gold Bug? Stop this Blob nonsense and forthwith get that deficiency sorted out: "Oh, my golly, Massa Will! ain't dis here my lef' eye for sartain?" roared the terrified Jupiter, placing his hand upon his right organ of vision, and holding it there with a desperate pertinacity, as if in immediate dread of his master's attempt at a gouge."
Another nice aspect of letterboxing/geocaching is that you are laying yourself open to total strangers whom you trust not to break certain implicit and explicit rules. If you leave a note-book and pencil and a few trivial tokens out in the wilds you can expect them still to be there after lots of other people have dogged your footsteps. I spent a few €€€s and a small amount of time a few years ago on post-crossing which allows you to sign-up to a web-site and get some random snail-mail addresses. You then send a post-card to a total stranger. For every card you register as sent you get, in due course, your own PC in the mail. It was kinda pleasant but it costs 90c to send a postcard To Foreign and I couldn't justify spending folding money on the off-chance of getting a picture of an office-building in Красноярск.
When the last GPS satellite burns up on re-entry, if there are still people on this our blue planet, they will still be setting each other letterboxing puzzles.