When skiers and snowboarders at Vail pick up one of the more than 200,000 pocket trail maps the resort prints each winter, they probably don’t know that the guy who will guide them through the fluffy bowls, glades, and wide-open groomers is a former house painter in Kingston, New York.

Gary Milliken, the founder and sole employee of VistaMap, has designed trail maps for more than 40 ski resorts in the United States—from Vail and Beaver Creek to Squaw Valley and Stowe—as well as 10 in Japan, 1 in New Zealand, and 1 in Italy. He has watched the niche field evolve from acrylic art to computer-generated works of precision, with the help of “personal research” that the 54-year-old ski bum never tires of conducting. Each map, rendered from a montage of Google Earth images, aerial photos, and on-location snapshots, earns Milliken between $3,500 and $15,000, depending on its complexity and whether it requires a summer version.

“When I first started this job 27 years ago, I used to do pencil sketches, then ship them over to Austria to be painted,” Milliken says. “Now, the way I describe the process to my clients is it’s like doing a painting, but the paint never dries. The illustration is alive. Every run, every tree, every window remains an individual object, and therefore can be changed.”

To create a new map, Milliken, who has produced Vail’s map since 1999 and Beaver Creek’s since 2004, starts by rendering a simple computer sketch of the mountain depicting primary terrain features like tree islands, lifts, and roads. Then he adds the details that fill our field of vision when we’re actually skiing there: buildings, rocks, AED stations, trail names. Throughout the process, he submits draft versions to the resort to make sure his depiction is accurate. “We’re able to basically fine-tune the thing almost in real time,” he says. When it comes to smaller updates, like adding the new Northwoods Express lift at Vail or the cookie cabin that debuted this season at Beaver Creek’s Red Buffalo Park, Milliken simply tweaks his computer creation.

Milliken, who holds a bachelor of fine arts from New York’s Parsons School of Design, calls himself “an artist at heart.” Accordingly, the fundamental challenge isn’t creating an aesthetically pleasing map, he says; it’s maintaining scale across the entire ski area and accurately representing different slope angles within tight space constraints. Luckily, he has become a master at simplifying complex terrain; witness his portrayal of the east-facing Stone Creek Chutes on one side of Beaver Creek, with the west-facing Royal Elk Glade on the other, telescoping multiple perspectives into one dimension. For this, credit his experience designing maps for amusement parks and zoos earlier in his career.

“There’s no way you can show the map from one view unless you’re super high in the air taking almost a bird’s-eye view,” he says. “It’s really about taking different views and figuring out where you can compromise by bending things around.”

This is where his personal photo reconnaissance and time on snow comes in handy. He has skied all of Vail and Beaver Creek, always on the clock, which he still gets a kick out of—even if he forces himself to stop and snap pictures more often than he would otherwise. “I don’t know if I have a favorite run at Vail,” he says. “I’m just happy to be at a huge place where I can explore.” And make a living carving turns, every ski bum’s dream.