TagPix: Automatic real-time landscape photo tagging for smartphones

This paper presents TagPix, a lightweight smartphone photo tagging app that provides good tagging accuracy, works in real-time, and protects user privacy. The main novelty of TagPix consists in leveraging the phone sensors and a place tag database to tag landscape photos which include landmarks. GPS location is used to identify landmark tags in a given region. Then, TagPix computes the angular distance for the object in the camera focus using the orientation sensors. This allows the app to select a small subset of landmark tags for the photo. For further tag accuracy, we devised new usable methods to estimate the Euclidean distance between the user and the landmark in the camera focus. These methods employ simple user actions and lightweight trigonometric calculations. TagPix is implemented and tested using several Android phones and Google Places API. The app was tested in 8 cities across USA. Using only angular distance, TagPix achieves 86% tagging accuracy. Adding Euclidean distance estimation leads to 93% accuracy.