NEW YORK — To plan an upcoming hike in the Alps, John Higham scoured scores of photos plotted along his route on a digital map for clues to the steepness of trails and the availability of accommodations or camp sites.

These images were just like other vacation photos shared by travelers and amateur photographers, except they'd been tagged with location information in an emerging practice known as "geotagging."

Armed with such data, Higham didn't have to search endless combinations of keywords and guess how photographers would describe images in captions. By zooming in on the map, he could easily find geotagged photos taken along the Via Alpina and gain a fresh perspective.

"I do like to see a place before I go, and study more about it," said Higham, 47, of Mountain View, Calif. "This affords me a way of seeing not just a map or satellite image but the landscape of where I want to go."

That's just one of the growing number of uses for geotagging, which is largely practiced by tech-savvy and professional photographers but is likely to expand. Global positioning is becoming omnipresent as more cell phones and digital cameras come with built-in GPS support.

"It's something that will become integral to the way digital imaging works," said Aimee Baldridge, a New York-based writer and photographer who tracks trends in digital imaging. "I think it's definitely headed for the mainstream."

TRAVELING ALONG

If a picture is worth a thousand words, a picture with geotagging can add a few hundred more.

Naturalists can map their bird sightings or chart out seal populations. Archaeologists can mark where they unearth artifacts. Travelers can wow family and friends and bring life to slideshows.

"When you add a map to a presentation, you've added another dimension, especially if you say, 'I took this great trip to China, and it was 5,000 miles over the course of a month' and they see a route," said Andy Williams, general manager of the photo-sharing site SmugMug Inc.

Higham has used geotagging to help friends and family track his yearlong journey around the world and a rafting trip later down the Colorado River.

For paintball competitions, Mitch Richardson of Salt Lake City geotags photos of an abandoned mining town nearby — he can mark places to hide and hazards to avoid on a map.

Typically, a photographer carries a standard GPS device that records location and altitude data every few seconds. That information then is matched with the time stamp on photos, using software like Pretek Inc.'s RoboGEO.

Devices that already support geotagging include some GPS-enabled camera phones from Sprint Nextel Corp. and a newly unveiled gadget from Pharos Science & Applications Inc. High-end cameras from Nikon Corp. and Ricoh Co. can directly connect to GPS devices, while the upcoming PhotoFinder from ATP Electronics Inc. will write GPS information directly on a camera's memory card.

And photo-sharing services like SmugMug, Google's Picasa and Panoramio and Yahoo's Flickr let you manually add photos to a map. Zoom in on New York's Central Park, for instance, to find individual photos taken at Strawberry Fields and other landmarks.

BETTER GADGETS COMING

Google extended geotagging to its YouTube video-sharing site last summer.

Professional aerial photographer Allan Goldstein gave up selling archival images from the Chicago area years ago, finding specific photos too cumbersome to locate on demand. He started the business again in October now that he can simply tag each image with its GPS coordinates.

But relatively few photos are posted with location information yet — Flickr estimates 5 percent.

There are privacy considerations, and the failure of satellite-dependent GPS to work reliably indoors. Also complicating matters is the fact that GPS devices tag the location of the photographer, while the landmark being photographed could be miles away (British entrepreneur Richard Jelbert attempts to solve that by embedding a compass that can help calculate the landmark's actual location).

But most importantly, geotagging still typically involves carrying an extra gadget and fiddling with software on a computer back home.

John Hanke, director of product management for geolocation services at Google, said he expects more camera manufacturers to include GPS this year and make it less cumbersome.

Dan Catt, senior software engineer with Flickr, sees huge potential as more people become aware of GPS and geotagging.

"That mainly comes down to GPS devices in cars and mobile phones raising people's awareness of location-based services," he said. "It wasn't really in people's consciousness even a year ago. ... We're very much at the beginnings."