Foursquare is cracking down on check-in cheaters.

It’s a crucial problem for the mobile, social service, which awards badges to users based on the number of times they log their location online, a process known as “checking in” to bars, restaurants, stores, and other venues. It hopes to make money by letting businesses give discounts to their most frequent visitors, known as “mayors”  — but that will only work if Foursquare can assure advertisers that its customers really are where they say they are.

The company’s chief executive, Dennis Crowley, said today that the startup will stop awarding points and badges if its app determines that the Foursquare player isn’t really where they say they are. Crowley said Foursquare users will still be able to check in from anywhere, but they might not get rewarded for it if they’re too far away.

That helps bring Foursquare in line with some of its other competitors like Gowalla and Loopt, which have stricter rules about checking into places that are at or close to your phone’s reported coordinates. That strictness, though, has made it tougher for them to sign up users. Since mayor offers are based upon check-ins, it’s important for the company’s data to be credible to its business and advertising partners too.

Crowley said the company has been experimenting with different ways of verifying where people actually are using “some GPS, the GPS accuracy reading, some elements of your [location] history, and a look at your check-in patterns.”

If it doesn’t seem like Foursquare user is really where they say they are, the app will nudge them with a prompt, reading “You’re a little far away.” People checking in through Wi-Fi may have some problems, but they can turn to Foursquare’s mobile web site. If the player uses SMS to check-in, the app won’t receive latitude or longitude coordinates but will work with a different set of inputs like a person’s history and frequency of checking in to guess if they’re being honest or not. All apps based on Foursquare’s application programming interface will work by the same rules, Crowley said.