About 10 years ago, the American military gave access to the high precision positioning system. Almost the same day, a man placed a box somewhere in Oregon, and posted the coordinates on a website. Geocaching was born.

Geocaches are currently placed in over 100 countries around the world and on all seven continents, including Antarctica. As of May 22, 2010, there are over 1,076,413 active geocaches around the worldWikipedia - Geocaching. With so many caches around the world, chances are there is several quite close to you. There certainly is many around Trondheim, and we started looking for them about a year ago. In total I've found a little over 30 caches, and at the end of this article is a map showing where they were located. You can easily check your local area too.

The official Geocaching web-site has a clever search page, where you can type in where you are in the address field. The results can then be viewed in Google Maps by clicking the link in the box above your results. Have fun!

Global Positioning System

GPS is not a new invention. The project was started in 1973 by the American Department of Defense, and is still maintained by the American military. It consists of several satellites that orbit the Earth, continuously sending signals down to our receivers. When the receiver picks up a signal it can calculate precisely how far away from that satellite it is. If you can pick up four (or more) of these signals you can calculate exactly where you are at the surface of the EarthGarmin - What is GPS?.

The figure shows an animation of Earth and the satellites. You can see how a point on the Earth sees multiple satellites simultaneously. Until 2000 the US only let civilians receive a scrambled signal, giving an accuracy of about 50 meters, but with this feature disabled the precision can be down to 3 meters. Sufficient to locate a small, hidden object.

Caches

When a person places a cache, he/she will note down the exact location from a GPS receiver. Later the location will be registered on the web-site, and people will be able to load the position on to their GPS unit. They can then go out and track it down. The cache can be anything from a very small box, with only a roll of paper to log your visits in (see picture), to large containers with things you can trade.

When you find a cache the most important thing to do is sign the log. There should always be a log-book of some kind. Later you will register your find on the Geocaching web-site, and your log entry is the proof that you actually were there. If there is something in the cache you would like, you can trade by leaving an object with similar value. The things you find are called loot, and depending on the difficulty of the cache it can be quite nice things. For example I got my LIVESTRONG wristband after we deciphered a particularly difficult mystery cache, in return I left a good fishing lure. It is customary to write in the log what you took, and what you left. Also, one usually thanks the owner with the abbreviation TFTC.

To make everything even more interesting, some objects have tracking codes. The tracking code is unique, and on the web-site each item has its own page. When someone finds it, and register the find, the objects page will be updated. A trackable object typically has a mission, created by its owner. For example: Take me to Australia, I want to see Sydney. Afterwards, take me back to Trondheim. Slowly, the object will move towards its target, from cache to cache. The objects can be a GeoCoin, or a dog-tag, called travel-bug, fixed to some other object. A fun game is travel bug races, where several people give their objects the same mission, and the winner is the owner of the object that reaches the destination first.

As I mentioned in the beginning, I have found about 30 geocaches so far. Not very many, considering the amount of caches around here. I've created a custom Google Maps map below that shows the caches I've found around Trondheim. Most of them have been found on longer trips with friends, where we set out to get 6-10 caches in one go.

Geocaching is great for many reasons. It might be the initiative you need to go hiking or just around your neighborhood. The caches are often placed at special places, with a great view or something else worth seeing. I've come across many nice places I'd never thought of going. Solving the mystery caches are perhaps the most fun part of geocaching. Some caches can be very creatively hidden, and it's a good feeling when you finally find it.

Most of all, geocaching is great because you can easily do it. Today many phones have good GPS receivers in them, and that is basically all you need. Visit the Geocaching site here, and see how many caches are located near where you live.