Combine high technology with old-fashioned hide-and-seek and you have one of the fastest-growing games for families and adventurers alike.

It's called geocaching, a treasure hunt of sorts, where players use high-tech satellite tracking devices to find caches of hidden treasure.

The game emerged five years ago when the first cache was hidden. Since then, it has literally exploded in popularity, with caches hidden in every state in the nation and in every country worldwide.

Geocaching works off a satellite system operated by the federal government. Originally for military use, the satellites broadcast a signal that can be picked up by a global positioning system receiver. When the receiver locks on to three or more signals, it can determine the user's location in longitude and latitude.

The signals were originally scrambled for civilians, but on May 1, 2000, President Clinton ordered the signals be unscrambled. The effect was to make the hand-held GPS units vastly more accurate, down to 20 feet or less.

Only two days later, the first cache was placed outside Seattle, Wash. The coordinates were posted on the Internet with an invitation for GPS enthusiasts to find it and log their visit.

Within days, several more caches were hidden and the sport of geocaching was born.

Ruth Papapanu of Sarver said she and her husband, Bob, have been geocaching for the past two years. The couple likes to travel and look for caches wherever they go."It' s been a lot of fun. A lot of times it will take you to places that you normally wouldn't find, because someone in the local area has found some neat place and puts a cache so people will go there," she said.Papapanu has found caches in several states including Missouri, Florida, Delaware, New Jersey, North Carolina, California and Washington.Papapanu said her funniest experience while geocaching happened while on a trip to Branson, Mo."I was in this business area, she said. "My GPS kept pointing me to this electrical shop. It has big windows in the front, but they're tinted."Finally, I go on the porch, and I see this piece of PVC pipe. On it are tiny letters that say GPS. I pick it up, and everyone in the store yells 'Yeah! You finally found it!' They were all watching me from behind the windows."Papapanu and her husband, in addition to finding caches across the country, have also hidden several local caches.She recently hid a cache along the Butler-Freeport Trail in Buffalo Township.

Slippery Rock Universitysenior Shelly Comer of Butler is another fan of geocaching. As a major in geographic information technology and vice president of the honorary geography society Gamma Theta Epsilon, Comer has participated in geocaching around the SRU campus."I have done a few (caches) through the geocaching Web site, but we wanted to get the students interested in it and try to familiarize some of the geography majors on how to use the GPS," Comer said of the club-sponsored caching events held on campus."It's fun for kids because it's more like a treasure hunt for them. When people ask me, that's what I tell them. It's a treasure hunt using a GPS unit."Today, the sport has evolved from basic hide-and-seek to a complex network and community. There are often cache events, which are get-togethers of geocache enthusiasts. The coordinates of the event location are listed on the Web, and the event itself is the prize.Another important event in the geocaching community is the annual Cache In-Trash Out day. During the April 16 event, geocachers worldwide helped clean up the natural areas where caches are often hidden.Geocachers have also developed their own niches. Regular caches are those that contain a variety of small items.When the cache is found, the player can take an item and leave an item of similar value and sign the logbook. The cache is then hidden in its original spot.Because caches are often hidden in public places, it's important to be discreet and not reveal their locations.Geocachers also have developed many varieties of caches. Microcaches - much smaller and more difficult to find - are usually in an empty film canister or candy tin.Multicaches are those that contain a series of clues at various locations leading to a final cache.Virtual caches are those that have no actual container; the reward is a historic site or unusual location.

The first stepin geocaching, is to purchase or borrow a GPS receiver. The receivers are available for about $100 in any sporting goods or department store.They are often purchased by hikers, hunters and other outdoor enthusiasts who might use the units in place of a compass.The next step is to log on to one of several Web sites that list coordinates.A search by ZIP code will no doubt list numerous caches and the coordinates of their locations. When the coordinates are entered into a GPS unit, the device can lead to the cache."My initial suggestion is to look for really easy- rated caches," said Jeremy Irish of Geocaching.com."Difficulty means difficulty in finding it. Take an area you are familiar with and once you get close to the location, put down the GPS and start looking."Look for parallel sticks, anything that looks unnatural," he said, noting caches are often hidden by sticks or rocks.A pioneer of geocaching, Irish founded the Web site in July 2000 after his first find using a GPS receiver borrowed from a friend."The thing that attracted me is that it's one of the few activities that start on the Internet and end up outdoors," said Irish."I think it's many things to many people," he said of the sport. "You don't have to be in the greatest shape to go out and find a cache. But you can also be an extreme hiker. It's something people can do as a family. It's accessible. And of course, who would not want to go out and do a treasure hunt?"

Irish said he still enjoys looking for caches, but now seeks out the more challenging adventures."I don't do the easy caches anymore," he said. "There are five levels of difficulty, and I like to do the high terrain. I do (fewer) caches, but I do the harder ones."Irish said his Web site originally listed only 75 caches. That number has now reached more than 167,000 and is still growing."It's interesting," he said. "You might walk past one every day and you have no idea."