The voice emanating from the iPhone was as soothing as the wind in the trees along Skyline Ridge Open Space Preserve in the Santa Cruz Mountains.
Duck down a tiny trail leading into the rocks off Sunny Jim Trail, the voice suggested. It leads to a slab of sandstone peppered with 3-inch-diameter holes where Native American women ground acorns in the rock mortars beside a creek.
The Midpeninsula Regional Open Space District audio tour is part of the latest trend in the outdoor experience. Once the purview of art and natural history museums, audio tours and digital guides bring history and science into the outdoors through smartphones, iPads and MP3 players.
Local environmental organizations and open-space agencies are producing their own audio tours, which allow users to see, hear, identify and plan their hikes from pocket-sized devices. Environmental Volunteers, Midpeninsula Regional Open Space District and Stanford University offer audio tours of the baylands, open spaces and campus flora and fauna.
Palo Alto company EveryTrail, a travel-guide website, has had more than 1 million trip guides downloaded from the site from people in 200 countries, company founder Joost Shreve said. Audio guides are the newest wave in enjoying outdoor travel, he said.
Just about anywhere one would like to go -- locally and throughout the world -- can now be explored through downloadable audio and digital guides. No longer just a voice droning through foam-covered headphones, audio tours through phones and digital tablets offer maps with well-delineated trails, pop-up photos at points of interest, slide shows, narrated stories and brief texts or videos.
"It's a way for users and parks to get interpretive messages for enriched experiences," said Renee Fitzsimons, Open Space District docent-programs manager. The district offers a 15-part tour of Skyline Ridge and Daniels Nature Center; the latter is a destination spot, she said. For those without digital devices, the tour is also available on MP3 players that people can borrow at the center.
Strolling around Alpine Pond, wood-rat nests are like apartment buildings that also house lizards and other small creatures, according to the audio tour.
Hamilton, who narrates the tour along with district biologists and docents, operates Audio Guides to the Outdoors, a production company in Berkeley that produces the tours. Outdoor audio guides help make better connections between people and their environment, she said.
"The more you know about a place, the more you're going to want to be there. All of a sudden you see things you didn't realize used to be there," she said.
An environmental journalist and former editor of Sierra Magazine, Hamilton developed the idea while in an art museum listening to an audio guide. She started the company in 2009, after she realized there wasn't anything to teach people about the outdoors, she said.
She has created a tour for Save Mt. Diablo and an auto tour of the Avenue of the Giants for the Save the Redwoods League. Users can download the redwoods podcast and listen to the tour as they drive, she said.
"I try to find people who know the place best," Hamilton said. For the Skyline Ridge tour, she interviewed Fitzsimons, district biologist Cindy Roessler, area superintendent Brian Malone and docents Sharon Thomas and Strether Smith. She does the recording outside, picking up the sounds of nature -- and an occasional airplane -- and adds voice-overs in her studio, she said.
Hamilton assembles interviews and creates an outline of the story she wants to tell.
"I will go to a place several times, take photos and record sounds to get an accurate soundscape," she said.
Audio tours that can be pre-downloaded to portable devices offer an advantage in remote areas, Fitzsimons said, where streaming an audio file or calling up a phone application might not work due to variable cell-phone coverage.
The medium particularly appeals to young people, who are already plugged into their phones and iPods, Hamilton said.
But audio tours could have a downside.
"There is a danger that people may put on their headphones and fail to listen to the nature around them. But that risk is worth taking because the information is there with you," she said.
Brittany Sabol, education and training director of the nonprofit Environmental Volunteers, calls the tours "augmented reality."
Instead of simply seeing "a pretty vista and nice-looking birds," the tours deepen people's understanding of what they're viewing, according to those who have used the organization's audio tour of the Palo Alto Baylands Nature Preserve, Sabol said. Produced by Redwood City-based Slow Life Games, the tour is available as an application through the iTunes store.
A trail map takes visitors from the entrance at Embarcadero Road to the ship-like EcoCenter, around the duck pond, through a fennel forest, mudflats, lagoon, boat dock, Lucy Evans Nature Center and the boardwalk. Users tap on a map area at each of eight stops. Tap on a topic in the page's top corner and one can view photos of duck pond migrants and denizens. Or listen to a brief narration about the creatures and their habitat.
Clicking on the "play" icon for "Rookery Ruckus," one will learn about black-crowned night herons and snowy egrets, whose unearthly calls emanate from as many as 40 or 50 nests in springtime, the narrator says.
With a flick of an index finger, one can flip through images shot by local photographers or read about baylands history. Sabol said there is enough content to use the application multiple times with a family. And teachers can take classes out to hike and learn about nature in various locations.
Especially important for families with children, each trail segment is marked with its mileage, she said.
Environmental Volunteers, which presents nature programs to students, would like to expand the tours to other hike locations, such as Los Trancos Open Space Preserve and Huddart Park, Sabol said.
Augmented reality has become a thriving business for Palo Alto entrepreneur Joost Shreve. When he started the website EveryTrail in 2006, there was nothing like it around, he said.
"I was traveling a lot and sharing my experiences online through blogs," he said.
Social media such as Flicker inspired Shreve to create a site for sharing travel photos when he moved from the Netherlands to the Bay Area in 2004.
"I started before the iPhone and Android were announced. I made a big bet on that," he said.
The bet has paid off. With advertising revenue, smartphone applications and professionally produced travel guides, Shreve's company, GlobalMotion Media Inc., was purchased by TripAdvisor in February 2010 for an undisclosed sum. TripAdvisor is the world's largest travel site and is owned by Expedia, Inc.
EveryTrail now has business relationships with Travel & Lesiure, North Face and REI. Shreve is the general manager.
EveryTrail offers thousands of digital guides, he said, but audio tours are just starting -- there are currently five podcasts and 11 guides involving audio on the site. In 2010 EveryTrail announced it was supporting audio in its EveryTrail guides for iPhones and Android and started a partnership with Massachusetts-based NaturePods, which has produced seven audio tours. There are also several of European destinations and tours by the California State Parks Foundation, Shreve said.
Those interested in nature can find guided tours for Bay Area hotspots and beyond on the EveryTrail site. A detailed hike up Yosemite's Half Dome contains text, video, photos and audio.
A guide for a drive around the Hawai'i Chain of Craters offers a large map, photos, descriptions of points of interest and tips, such as bringing a good supply of water and lunch, as there is no food available. Chapters include stops from the top of Kilauea to a drive through amazing lava flows and the Pu'u Loa Petroglyph Trail. Each section has photos, videos and a separate detailed map, directions and three-day weather forecasts.
The enjoyment of digital tours does not rest solely with those who download the files. Increasingly, travel and nature enthusiasts are creating their own tours, and EveryTrail tries to make it easy. The site offers templates.
Users can also upload information in real time. They can plot routes on maps, take and post photos and add a text that can be uploaded to Facebook and Twitter.
"You are in total command," Shreve said.
Type in "Palo Alto," and there's a hike around the Palo Alto Airport, a Baylands run, Shoreline hike, mountain biking in Arastradero Preserve, and a Stanford University campus walk.
"This is the short version of our Saturday Morning Bakery Ride," a Palo Alto resident wrote of a trip called Woodside Bakery Ride, in which cyclists ride from Palo Alto to Woodside and then sometimes travel as far as the coast. The site shows a map with the 31.7-mile route plotted in red. Clicking on a point on the map starts a slide show of photos the resident took along the way. A blue cursor automatically moves along the route to indicate where each photo was taken.
Sometimes, the guides strive to give the "inside scoop."
"It wouldn't be out of the ordinary to see Joan Baez at Roberts," the cyclist wrote, showing a photo of the assembled cyclists outside Woodside Bakery.
"More typical, though, is a blonde wearing running clothes, talking on her cell phone or walking to her black SUV."
Indra Singhal has used EveryTrail since November 2007 to find trails and even follow his favorite hikers to new and interesting places, he said.
"I've been a very early user of EveryTrail. It's a remarkable repository for information. I use it whenever I go into a new trail," he said.
In the early days, he tracked his trips with GPS. But with his smartphone, Singhal said, he no longer has to do the mapping. He can turn on the phone's tracker and just upload photos along the way that sync with the locations on his map.
Whenever he is looking for a particular kind of hike, he uses EveryTrail, he said.
"The Bay Area is just jam-packed with nature trails. I don't think you can travel all of them in a lifetime," he said.
He also uploads his own maps and guides.
Last weekend he took a trail to Black Mountain, but he wanted to start it on State Route 35 (Skyline Boulevard) rather than Page Mill Road. Nobody else had mapped it from that side, so he started recording the hike from that spot using geotracking. He added photographs along the trail route so that others would know what to expect, he said.
A link includes an enlarged topographic map with the plotted route and brief commentary about what he found along the way: breathtaking views, crossing a series of small creeks, three wooden bridges over Stevens Creek and strutting wild turkeys.
"The next guy who wants to do it, if a trail exists, with one click, can download it to a smartphone," he said.
He has also turned a particularly strenuous hike along Limekiln Trail to Priest Rock and Kennedy Trail in the Sierra Azul Open Space Preserve into a guide, he said. It has been viewed 3,301 times.
Singhal, who has downloaded many podcasts and audio tours in museums, said he is excited by the addition of nature-related audio tours.
Shreve said he expects the industry to only grow as refinements are made. And audio tours will continue to grow in popularity, he said.
"Photos, videos and audio create a lively experience," he said. "It's a key thing. People love to show off what they are doing."
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