But if you are a technology lover with a taste for the open air, this doesn't describe a seemingly impossible task. Instead, it describes a hobby rapidly gaining fans among the gadget friendly. The hobby goes by the name of geo-caching. And it is the latest outgrowth of a specialised form of leisure activity known as hacker tourism. Those finding the treasure in this way are supposed to take something out, put a new item in its place, sign the visitors' book and move on.
Items left in caches include CDs, soft toys, sweets, money, pictures, and tools.
The handset uses signals from the constellation of 24 satellites, which make up the Global Positioning System, to work out where you are on the planet. Indirect approach Finding a location on Earth is done by working out very accurately how far someone is from at least four satellites. Secreted between large rocks, this cache will require long arms and a little stone rolling to find. The distance between the satellites and the person on the ground is measured by timing how long it takes a signal to travel to the GPS receiver that person is holding. The distance is enough to make a hunt for an exact location of a small box frustrating, especially if there is a big geographical feature in the way that means a direct approach to the cache is impossible.