Study: Three-quarters of smartphone owners use location feature

That means that the portion of Americans using their phone to track their location has nearly doubled over the last year, to 41 percent.

The study also found that 18 percent of smartphone owners use a social service such as Foursquare to "check in" at locations.

While being able to quickly find directions or nearby restaurants can be helpful, the fact that so many people now carry a location-tracking device with them at all times has also raised privacy concerns.

The American Civil Liberties Union (ACLU) released a report last month that found that local police across the country regularly gather cellphone location data, often without a warrant. The ACLU called the practice "pervasive and frequent."

Sen. Al FrankenAlan (Al) Stuart FrankenShould the Rob Porter outcome set the standard? Grassley, Dems step up battle over judicial nominees Sen. Gillibrand, eyeing 2020 bid, rankles some Democrats MORE (D-Minn.) sent a letter to Attorney General Eric HolderEric Himpton HolderPavlich: The claim Trump let the mentally ill get guns is a lie Pennsylvania Supreme Court releases new congressional map 36 people who could challenge Trump in 2020 MORE on Thursday, requesting that he explain the Justice Department's practices for collecting location data.

Privacy advocates were outraged earlier this year about a mobile application called "Girls Around Me" that allowed users to find the location of nearby women by scanning publicly available data on FourSquare. The app also included information from the women's public Facebook profiles. The company behind the app pulled it after the public outcry.