Magazine article American Forests

Geocaching: Trees as Treasure; Affordable GPS Units Are Creating High-Tech Scavenger Hunts for Everything from Dollar-Store Trinkets to Trees. (Recreation)

Magazine article American Forests

Geocaching: Trees as Treasure; Affordable GPS Units Are Creating High-Tech Scavenger Hunts for Everything from Dollar-Store Trinkets to Trees. (Recreation)

Article excerpt

"Do you have a GPS?"


"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. …

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