Geocaching: trees as treasure; affordable GPS units are creating high-tech scavenger hunts for everything from dollar-store trinkets to trees. (Recreation).

"Do you have a GPS?"

"Yes"

"Do you know anything about 'geo caching'?"

"Uuuuuuuuuh... no."

A few days later, as I find myself stumbling, splashing, and tripping my way through a heavily forested floodplain, I'm getting a pretty good idea what the "sport" of geocaching is all about. I'm in search of a birch tree growing near the banks of a sleepy, winding ribbon of water known as the Willis River in Virginia. For good measure I carry with me two Global Positioning Satellite (GPS) receivers. The plan is to find not just any birch, but a specific river birch and establish its GPS coordinates.

GPS, as this form of navigation is commonly known, is based on a network of satellites, each broadcasting a synchronized signal. The GPS receiver determines its position on earth by comparing the arrival time of each incoming signal. Then, it mathematically computes a location, It's so accurate, in fact, that during the Iraq war GPS-guided bombs were used to destroy not just individual buildings, but distinct areas within those buildings.

Buried in the heart of Virginia's Cumberland State Forest, the birch I seek is special. Due to its overall size, the birch has long held a spot on the state list of champion trees (the largest-known of each species based on AMERICAN FORESTS' National Register of Big Trees' formula of height, circumference, and crown spread). But it's been 10, 15 years or more since anyone last saw this champ.

With a faxed copy of a hand-drawn map to guide me through the maze of narrow channels and thick brush, the odds of finding the birch grow dimmer with each unexpected detour. The high-tech navigation devices I carry are not much help at the moment. All they can do right now is tell me how to get home--or, rather, back to the car--which at this point is a welcoming thought.

At long last a massive birch tree suddenly appears almost out of nowhere. If it hadn't been for my companion, I would have walked past it even though it was only a few steps away. Just because something is big, doesn't guarantee you'll find it if you're dodging sticker bushes in your face. Besides, either it's not where it was said to be or I'm not where I think I am. It won't be long before I realize it's a little of both.

Even though we're sure we've found our birch, we search another 20 minutes to make sure it isn't a fraud. Once all doubt is erased, I punch a button on the GPS while standing at the foot of this massive tree and a decimal version of latitude and longitude is frozen on the display.

Back at my office, I log onto a website that allows me to overlay my coordinates onto a U.S. Geological Survey (USGS) map so I can compare the faxed, hand-drawn map to what the GPS reveals. The hand-drawn map is part of the standard form used to nominate a tree for Virginia's list. The birch was selected for my search partly because it's on public land, and therefore accessible, and partly because it has a detailed map. But the website's map reveals the tree significantly northeast of its hand-drawn position. Worse still, after all the mind-numbing detours, it shows that I wasn't where I thought I was, a fact that could help explain the original mapping error. To be sure the GPS is correct, I compare the hand-drawn map to details revealed by aerial photographs, a 1:25,000-scale USGS map, and my experience on the ground.

With a few mouse clicks, a link to the map showing the tree's position is e-mailed to Jeff Kirwin, state Big Tree coordinator, at Virginia Tech. His immediate response: "The links are outstanding! Can we link them to our website?"

The sport of geocaching is perhaps best described as a high-tech scavenger hunt in which computers and the Great Outdoors come together. According to the official geocaching website, the sport took off in the Pacific Northwest when, on May 1, 2000, the Clinton administration allowed civilian use of highly accurate GPS signals that had previously been reserved for the military. Within days, the first "cache" was established near Portland, Oregon, and its coordinates listed on an internet newsgroup for GPS users. A few months later, the name "geocaching" was coined when a couple of guys in the Seattle area established an official website (geocaching.com). Like a computer virus, the sport quickly spread across the nation and jumped oceans.

The first caches were--and often still are--little treasure troves containing knickknacks, log books, and even disposable cameras so those who find the cache can prove they were actually there. There are also "virtual caches" in which the destination is the sole reward. Folks who find a cache are encouraged to relate their experiences on the geocaching.com website.

Like everything else in the computer world, the sport continually evolves and new variations appear constantly. Some geocaches are part of a game and others are educational or historical. In fact, it was one of those evolutions that led me to the banks of the Willis and the massive river birch.

Jenn Seva-Kutch and her husband are confessed outdoorsy types in the Philadelphia area. She parlayed that love and a GPS she won into a new pastime. For her, geocaching "is an excuse to take a walk outside. It gives me some direction and encouragement to see places I hadn't seen before."

Near her home she recently stumbled on a cache called "Family Tree." What she found was a white birch listed on AMERICAN FoREsTs' National Register of Big Trees. Intrigued by her find, she contacted AMERICAN FORESTS to see if other champions were nearby. It was Jenn's inquiry that led to my early spring stomp in the woods and to changes at AMERICAN FORESTS as the organization realizes the benefits GPS coordinates can offer.

"It's another tool for people to go and enjoy the majesty of our big trees," says AMERICAN FORESTS VP Karen Fedor, who runs the Big Tree program. "We get a lot of inquiries from folks wanting to know where to find the big trees." As luck would have it, a GPS manufacturer recently donated five GPS receivers to the organization. These units will be distributed to state Big Tree coordinators to help them create a GPS database of significant trees.

Fedor says AMERICAN FORESTS plans to post the GPS coordinates of as many of the big and historic trees as it can while keeping in mind certain considerations. "You have those public and private land issues," says Fedor. To post the coordinates, AMERICAN FORESTS needs the cooperation of the landowner, whether a private person or a public agency. Many private landowners, while happy to cooperate, do not want the public to invade their land. Some governmental bodies feel the same way.

"We don't want it here," says Cindy Lane, deputy manager of the Dismal Swamp National Wildlife Refuge, which is home to the national champion swamp tupelo. When asked if it would like to be the first virtual cache on the Big Tree list, the refuge said no thanks.

"We consider geocaching to be incompatible with the refuge mission," Lane says. The refuge fears too many people off the trails and damaging the swamp. It's an concern Fedor understands.

"When you go off-trail, you open a whole new can of worms" including erosion problems and plant destruction, she says. Such concerns are addressed strongly on the geocaching website. Any cache found to be causing environmental harm is immediately removed.

Wildlife refuges are not the only ones discouraging geocaches. The National Park Service and other organizations forbid them. But some states, like Pennsylvania and Virginia, are embracing geocaching--with some caveats.

"We encourage the participants to work with park managers so as not to damage the natural resources," says Jim Meisner of the Virginia Department of Conservation and Recreation. "We want them to work with managers in placing caches on trails that are accessible, safe, and have minimal impact on the environment."

In neighboring Maryland, an unannounced cache was left inside an old ammunition can in a state park. When park employees found it, the FBI bomb squad was called and $30,000 in state money went up in smoke. In Pennsylvania, the department of conservation and natural resources has gone so far as to post geocaching guidelines on its website www.dcnr.state.pa.us/geocaching.htm.

After realizing the potential problems that could arise from a blanket posting of Big Tree coordinates, Fedor says "we're gonna start out small and focus initially on five to 10 trees. We'll list first on public lands and trail-accessible trees."

Now that you have a good idea of what not to do, here are some ideas for chasing down a champion tree, especially one buried deep in the forest--once you're sure it's OK for you to go there.

First, get a map. Even if you have GPS coordinates, you don't have all you need to know. You can log on to a site like TopoZone.com and, with your coordinates, get a USGS map. I find the 1:25,000 scale to be the most helpful. It might be a good idea to check out Mapquest.com to get you to the general area of your search. If you're an information junky, you'll probably want the aerial photographs you can get at www.terraserver.microsoft.com. At the 32-meter resolution, you can easily see entire towns. At 1-meter resolution, you can count cars in the parking lot! You may also find your USGS map easier to understand when you compare it to an aerial photograph of the same site.

Another reason to get a map is the following self-discovered corollary: The odds of battery failure are equal to the necessity of the device in which they're used. You don't want to be out in the woods with a dead GPS, so carry extra batteries. And you might want a compass to keep them company. If you're a klutz like me, you stand a good chance of dropping your GPS and stepping on it while admiring the overhead canopy. Or, if you're staring at the display while you walk, you'll stumble like I did, repeatedly, and nearly drown it in water or smash it into the ground under your hand.

Geocaching may seem too easy at first; after all, you just punch the coordinates into your receiver and it tells you which way to go and how far. It will probably come as a surprise when you discover that just because the GPS says "go this way" doesn't mean you'll want to or that it's even possible. Rivers, cliffs, swamps, and sticker bushes have a nasty habit of getting in the way. Again, a map can save you some potential headaches. Finally, make sure you can legally be on the land. Just because you can get there doesn't mean you're welcome.

Now that you're all excited, you'll probably wonder which brand of GPS to buy. As a pilot and techno nerd who's worked with GPS for years, I trust Garmin and Magellan. Each company offers various units with lots of whistles and bells costing from about $100 to $1,000. Of course a whole slew of accessories are available. The two units recommended by the geocaching website, Magellan GPS 315 and Garmin eTrex GPS, are the ones I had for this project. Of the two, I preferred the Magellan.

Now if you want to know more about how a GPS really works... well, that's another story for another time.

Photojournalist Tim Wright maintains GPS coordinates in Richmond, Virginia.