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For the past eight years, Wallace—who goes by "WallyGPX" on his chosen platforms—has been a "GPS artist," drawing his creations Etch-A-Sketch-style with tracks of global positioning data left by his bike routes. Wallace is one of a collection of early adopters of fitness tracking apps who discovered that they could turn their runs, bike routes, and other tracking data into a form of geeky, sometimes subversive self-expression.

Wallace told Ars that his interest in GPS art grew out of his initial dabbling in geocaching in 2010. "My cousin turned me onto geocaching," Wallace recounted. "And I had this eureka moment where I said, I wonder if I could use the phone to install an app to draw my name on the city. And for about 30 seconds, I thought I had found something original."

He quickly found he wasn't alone. And over the past 8 years, GPS art has become, well, a very mainstream thing—Old Spice even turned it into a marketing campaign. And as apps like Strava have made social sharing of geospatial tracks easier, they've fostered a small but growing community of people who turn satellite navigation into virtual global graffiti.

Even airplane pilots have gotten into the act. Long before Navy pilots flew phallic patterns in the sky over the Pacific Northwest this past year, other aviators were leaving tributes and messages in their flight plans (though dick-shaped flight patterns have a relatively long history). The audience for those artistic flight paths has gained a bigger audience thanks to ADS-B transmissions and services such as FlightRadar24, which devotes some attention to "skydrawing" and other ADS-B based art in its blog.

The tools of the trade

Each GPS artist has their own preferred tracking app. Strava is the tool of choice of Stephen Lund (AKA "Cycleangelo"), a cyclist-GPS artist in British Columbia who publishes the epic-length GPS "doodles" he creates on his road bike both on Strava and on his blog. Some of Lund's rides close in on 100 miles. Claire Wyckoff, a comedy writer who specializes in phallic running routes (and may have had some involvement in the Old Spice Dream Runner campaign), uses the Nike+ tracker. And Wallace uses four apps at the same time, for both redundancy and aesthetic choices—he says each app's map has a different look.

"Right now, my favorite is Strava—because it has a social aspect to it—get lots of people who comment on it," explained Wallace to Ars. "I also use MapMyRun, and I've added RunKeeper. The one that I liked the best out of all of them is now unsupported, and that's My Tracks—My Tracks accounts for seasons 1 through 6, and after season 6, I started using Strava."

Each work begins with a ride plan, prepared by tracing a pattern over a Google Maps printout, with notes on where to take every turn. Wallace then mounts the plan on an alligator clip to guide him along his routes, some which run up to 20 miles—not an easy spin on a mountain bike on the streets of Baltimore.

"I'll look on Google Earth sometimes to make sure the pathway exists, especially when going through uncharted territory," Wallace explained."But I literally know every square inch of Baltimore where I ride now." Sometimes that's the result of road hazards. Flats caused by broken glass have left him to push his bike for the rest of his routes. He recently cracked the frame on his latest 29-inch wheel mountain bike after putting 3,000 miles of street wear on it.

"When I'm done, I take screen caps of them on my laptop or my phone itself," he told Ars. "And I'll crop it and I'll digitally sign it and put it out on the Internet for people to gawk at." The first tracking app he found, called MEGL, didn't show the track while it was in progress—"You would have to make it, hit save, and the map would pop up afterward," he said. "The first one I did, I spelled 'Wally' across the city. And I pulled over on the side of the road, and in this sweaty moment I looked at my phone and [hit save] and saw that it had worked. In that moment, I realized if I can do this, I can make anything. So I started to make everything."

Over the course of the summer of 2010, he made 25 more GPS sketches. "The first 10 were really special," he said, "because of the unexpected outcomes and the big reveal at the end." The vagaries of GPS reception added to the surprise. "I learned I could get these things I call bounces, signals that would bounce my track into someone's porch... they also make these extremely authentic. It's all the whim of where you're going, and the conditions around you, the satellites that are connecting to the tech in your pocket."

Wallace's exploits have, over the years, led him down some unexpected alleys, both literally and figuratively. He's also been chased by dogs, and he has drawn a few suspicious looks for his strange cycling patterns. But his rides have also gotten him some local and national media attention and have earned him speaking invitations at events such as Bike Hack, an annual event put together by the National Academies' Transportation Research Board. And it gives him a platform to talk about creativity with students.

Plus, he gets a lot of exercise.