I'm not going to get into the details of GPS here... Joe Mehaffey and Jack Yeazel's GPS Information website is where you want to go for that. For those completely unfamiliar with the concept, there are a series of satellites in orbit sending signals down to the surface. Using an electronic device no bigger than a cell phone you can pick up these signals and, with a little mathematical magic, determine your precise position on the Earth. Pretty nifty. Most receivers have all kinds of features and functions, but, again, I won't go into that here.
I bought a receiver in late April 2000. This was fortunate because in early May the Dept. of Defense turned off a "feature" of GPS that intentionally degraded the signal coming from the satellites (called Selective Availability, or SA). This was to prevent our enemies from using our own positioning system to pinpoint bombs against our nuclear missile silos (which require a direct hit to disable). The DoD now has other measures for defense, and so now our receivers are suddenly 10 times as accurate. Accurate enough to find buried treasure...
With the demise of SA, it was possible to take a pair of numbers (latitude and longitude) and get within a couple of meters using a GPS receiver. A game called "GPS Stash Hunt" was born, later named "Geocaching". The idea was simple. You create a cache of goodies, consisting of at least a log book, and hide it somewhere...anywhere... anywhere on the face of the planet. You then publish the latitude and longitude of your cache, and people from all over the world can try and find it with no more than a $100 electronic device. Most of the caches contain goodies or mementos that you can keep, but it's polite to leave something if you take something thus keeping the cache stocked for the next person. The log book lets you write down your adventure in finding the cache, and you can read the adventures of others, where they are from, etc. Once you have signed the logbook and traded any goodies, please leave the cache just as you found it... replace the lid and any covering material, etc. If you have contact information such as an e-mail address for the person who placed the cache you might drop them a note to let them know the status of the cache in case it has been damaged, vandalized, removed, etc.
Similar games of "hide and seek" have been played for many many years, such as Letterboxing that uses elaborate clues and directions, but this is the first game where nothing but two numbers are required to find the goal.
I have placed a couple of caches in Manistee National Forest with plans for a couple more in the area. They are in 12" diameter plastic buckets, buried to within an inch or so of the top, and sealed with an unmarked black lid. Due to the surrounding trees, they may be covered with leaves or other debris so you may have to do some good old-fashioned searching for them once you get in the general vicinity. I suggest you do some initial homework to find out what sort of terrain you'll be getting into. All coordinates are in the WGS84 datum.
Clicking on the coordinates above will let you see the distance of all known Geocaches in relation to the one you selected. For more information about Geocaching you can visit Mike Teague's original GPS Stash Hunt (Geocache) page.
It's unfortunate, but I feel it's necessary:
Disclaimer: You are under no obligation to hunt my Geocaches. Use your best judgment with the environment and conditions and remember that, like all outdoor sports, there is an element of risk. When/if you find a cache, you are under no obligation to open it. Open at your own risk. If food or drink is present, do not consume if the safety seals are broken; if they are, do everyone a favor and dispose of the items.