A secret Apple iOS app has been discovered on the App Store. "Indoor Survey" does not appear through a traditional search, but the app can be accessed through a direct link. First spotted by developer Steve Troughton-Smith, the app uses signal data and the iPhone's sensors to map out indoor venues and enable indoor positioning.

"By dropping 'points' on a map within the Survey App, you indicate your position within the venue as you walk through," the description reads. "As you do so, the Indoor Survey App measures the radio frequency (RF) signal data and combines it with an iPhone's sensor data. The end result is indoor positioning without the need to install special hardware."

Apple's mapping efforts have in the past left something to be desired. The company famously apologized for switching away from Google Maps with iOS 6 in 2012.

Since the fiasco, Apple has made great efforts to improve the quality of its maps. Last October's launch of Maps Connect invited small business owners to improve their Maps, prioritizing public venues with over one million annual visitors. With iOS 9, Apple has expanded its map offerings to include transit directions, which like "Indoor Survey" also includes navigation options for indoor locations.

Apple makes a limited amount of iPhone apps available through its own App Store, with only 16 apps shown on the store page at the time of writing. Apple has a history of bundling apps with stock iOS if it feels the functionality is crucial to a core iOS experience, which has led to some complaints that the basic OS comes with too many extras.

Don't expect "Indoor Survey" to make an appearance on the next iOS, however. The app's limited use means it is likely to stay off regular consumers' devices.