ST. PETER — Geocaching is a treasure hunt using high-tech tools — or as one geocacher noted, using billion dollar satellites to find Tupperware.

After Bill Geary of St. Peter retired in 2005, his wife bought him a GPS. “That started me,” he said.

An enthusiastic participant of geocaching, Geary (aka Ramsey63) has found 1273 caches in two years. “I’ve done all the rest areas between here and New Jersey,” he said.

Ramsey63 has measured the flow of a creek, deciphered bar codes, boated to an island in Lake Jefferson and translated Swahili — all to find the longitude and latitude coordinates to plug into a GPS (global positioning system) to find hidden caches.

Finding the cache is the reward.

Most beginners try to find regular caches without solving puzzles using GPS coordinates found on the Internet. These caches contain a logbook, and usually a few trinkets for trade, in a weatherproof container.

These treasures can be just about anything, but usually are coins, pins, cards, key chains or small toys. Once the stash has been located, the finder signs the logbook. If a treasure is taken out, it is replaced with something else.

“I love it,” said the geocacher known as International Family, who has found about 50 caches.

But for Jo E. Anderson, a retired physician in Le Sueur, the fun is teaching geocaching in a Le Sueur Youth Opportunities program.

Anderson takes his geo-kids on field trips to find caches. “Kids are really into this,” Anderson said. “They have the ability to think outside the box.”

Geocachers also hide caches for others to find. This year Anderson’s students planted a travel bug in a cache. A note attached to a toy zebra states, “My name is Zebbie the zoo zebra and my mission is to travel to zoos.”

“The program allows us to be contacted by e-mail when the zebra goes to another place,” Anderson said. Since July Zebbie has traveled to caches in St. Peter, near the Chicago zoo, Missouri and then close to the St. Louis zoo with the help of cachers who find the zebra in one cache and take it to another.

The hunt for caches usually starts at the game’s main Web site, geocaching.com by entering a ZIP code or city. A list of caches in the area pops up on the screen. For example, there are 86 active caches within 20 miles of Mankato.

Although the GPS determines the general location, identifying the specific location becomes the challenge. A GPS can have a margin or error up to 20 feet, Geary said. “It’s taken me to a lot of interesting places.”

Discovering and learning is part of the sport. The search for one cache led Geary to the Arlington Cemetery tombstone of one of the men who caught John Wilkes Booth.

“It’s a great family sport,” Anderson said. He wants to expand his geo-kids into a family geocaching club.

Mike Omtvedt of Madison Lake started geocaching about five years ago when he “was looking for something different to do with his kids.” A friend introduced him to the sport.

Now Omtvedt teaches Boy Scouts how to use GPS handheld units in orienteering. “We use geocaching as a way for scouts to practice their skills,” he said.

“Probably the great value of geocaching is getting kids outdoors, steering them away from computers,” Omtvedt said.

Most geocaches involve a hike, usually in a park. The idea is that getting to the cache should be as enjoyable and rewarding as finding the cache.

Until two years ago the Minnesota Department of Natural Resources did not allow caches to be hidden in state parks. Now they can, but with restrictions posted on the DNR’s Web site. Minnesota has almost 6,000 caches.

Most Minnesota geocachers have found caches posted by King Boreas, who has hidden more than 1,500 caches with several in the Mankato area.

Tomslusher, which is a geocacher handle, is another well-known geocacher in this area. “He has a dandy puzzle to figure out the coordinates using wristwatches and sun dials,” Anderson said.

Being the first to find (FTF) a cache receives special recognition. “Ramsey63 was the first to find all of the geocatches we’ve hidden,” Anderson said.

Nanocaches are less than a half inch, with only a tiny logbook. “I found one, a magnetic thing, that was painted red and attached to a stop sign,” Geary said. Other sizes range from microcaches, usually a film canister, to larger ones up to 4 feet tall, such as ammunition boxes.

Variations on the game include Webcam caches. The idea is to get yourself in front of the camera to log your visit. Geary found one in Grand Rapids, called his sister in Hawaii who went to the Webcam’s computer site, and took a picture him on her monitor. “Then you publish the picture to prove you were there,” Geary said.

Some caches called “multis” link a series of coordinates with clues to reach a final destination. “There is a new one at Minneopa Falls,” Geary said.

A virtual cache is one where the seekers must answer a question from a landmark to verify they were physically at the location. The sign noting the high water mark of a flood in Seven Mile Creek between Mankato and St. Peter is a clue in one virtual cache, Geary said.

Geocaching even has its own lingo. Posts include references to Muggles (non-geocachers, just like nonmagical people in Harry Potter books), hitchhikers (travel bugs) and a number of acronyms.

The popularity of geocaching has grown rapidly since it began May 3, 2000, when Dave Ulmer hid a can of beans and other treasures near Portland, Ore., to test the GPS signals the government had just opened to the public. There are now almost a half million caches hidden in 222 countries.