The mobile phone as a platform for assisting the independent living ...

Chapter 6Implementation of an indoor localizationsystem based on mobile phone’s cameraWe propose an indoor localization mechanism that relies image matching to locate amobile user (scene analysis technique). The benefit of this approach lies in its ability tolocate the user without the cost of additional hardware.6.1 OverviewWith this application we explore the possibility of determining user’s location indoorsbased on what the camera-phone “sees”. The camera-phone is worn by the user as apendant (Fig. 7), which captures images periodically and sends them to a web server overFTP. The web server maintains a database of images associated with their correspondinglocations. Upon receiving an image, the web server compares it with stored images, andbased on the match, estimates user’s location. We accomplish this with off-the-shelfimage matching algorithms, by tailoring them for our purpose. We built an imagedatabase for a small apartment with nearly two hundred pictures to account for real-lifeissues such as varying heights of the users, different angles that may correspond to thesame image, etc. The key advantage of using this approach is that it does not require anyinfrastructure. Neither custom hardware, nor wireless access points are required. Physicalobjects do not have to be “tagged” and users do not have to carry any device apart fromwhat they usually do: a mobile phone. The only cost involved is that of building an imagedatabase.32