Jetpac City Guides, a free, new iPhone app, skips user reviews to analyze data from billions of publicly shared Instagram photos to offer tips on everything from hip bars and hot coffee shops to cool music venues and popular museums.
"We learned that people love browsing their friend's travel photos, but their friends hadn't been everywhere," said Jetpac co-founder and CEO Julian Green.
(Read more: Road Warrior read-in)
The company mined Instagram photos for clues about where people went and what they liked to do.
"Think of a photo as saying, "I'm here and I'm taking a photo,' " Green said. "That's a strong recommendation for the fact that someone is having a good time. It's like check-in or a review, a very data-rich review."
Jetpac worked through the Instagram developer program and created an image analysis that uses an algorithm to parse each photo down to the pixel. It looks for patterns and assigns value to details such as the amount of blue sky, the evidence of coffee cups, lipstick, or mustaches, and the presence of beaches or wine glasses.
(Read more: Man locked in cabin)
From these and thousands of other data points, Jetpac puts together lists such as "Hipster Hangouts in San Francisco" and "Bars Women Love in Moscow," Green said. It has also figured out popular "go to" places in 5,000 cities. They include bars where business travelers gather, places where dog people hang out, restaurants with the best views, and favorite places for outdoorsy types, parents (with and without their kids) and sports fans.
"Other polls ask people how happy they are," Green said. "Our study reveals what people show."
Showing is good, because when people take leisure trips they use photos to help them decide where to go, stay and eat, and what to do, said PhoCusWright research analyst Maggie Rauch.
But research shows that people also use photos less frequently than some other tools, such as interactive maps, traveler reviews, and professional ratings and photos.
"What seems important to me is if [Jetpac] integrates with helpful reviews and can get people to use the app in their own city," Rauch said. "But they would be up against some pretty strong established players," she added, including TripAdvisor, which bought photo-heavy site WanderFly last year, and Yelp.
One thing Jetpac has figured out is where people look the happiest. By studying the average size of people's smiles in more than 100 million Instagram photos, it has come up with a list of the 50 happiest U.S. cities
The five cities with the highest "smile scores" were, in descending order, St. Louis, Mo.; Kansas City, Mo.; Columbus, Ohio; Indianapolis; and Pittsburgh.
That's useful information for a travel app to offer, said Green "because people like to go where other people are happy."
(Read more: Middle class priced out of skiing)
Perhaps oddly, Anaheim, Calif., home of Disneyland—the self-described "Happiest Place on Earth"—ranked last on Jetpac's list.
—By Harriet Baskas, special to CNBC.com. Baskas is the author of seven books, including "Hidden Treasures: What Museums Can't or Won't Show You," and the Stuck at the Airport blog. Follow her on Twitter at @hbaskas.