Apple has acquired a Silicon Valley indoor mapping start-up for $20m, the Wall Street Journal has learned.

Apple stopped offering Googles map as standard on its handsets last year in favour of pushing its own technology. Its acquisition of WifiSLAM, which uses wi-fi already on offer in shopping centres and airports to help locate people where GPS fails, will help the company move indoors.

The space is becoming increasingly crowded as brands, venues and tech providers see the potential of indoor location-based mobile marketing campaigns. While Google and Microsoft already offer some indoor mapping solutons, a location alliance formed by Samsung, Nokia and Qualcomm has committed to providing indoor location services this year.

French company Pole Star has been working on an indoor mapping solution with map provider Micello which is based on a similar use of wi-fi. French Connection recently started trialling the Retail Mesh wi-fi platform to help them monitor footfall and send SMS to opted-in users when they enter a store.