Survey of Landmark-based Indoor Positioning Technologies

Owing to the increase in the time people spend indoors, coupled with the pervasiveness of high-performance smart devices, the importance of indoor positioning techniques has grown. Researchers have extensively studied indoor positioning techniques using wireless signals or mobile device built-in sensors because satellite signals are absent in indoor environments. However, the built-in sensor readings tend to be distorted by the surrounding indoor environments. Furthermore, wireless signal-based technology incurs substantial cost because of presurvey and maintenance. To address these drawbacks, landmark-based indoor positioning technologies have recently been developed. An indoor landmark is a unique point in a room that is distinguishable from other points based on its features. Because the indoor landmark itself underscores the unique features of a specific region, it acts as a reference point to help users navigate efficiently. In this paper, we review recent landmark-based indoor positioning technologies. We categorize the technologies according to whether they use wireless signals, built-in sensors, images, and multisource-based technologies. We analyze them based on six evaluation criteria, namely, accuracy, core technology, detection difficulty, cost, versatility, and robustness. Finally, we discuss future directions of research and applications on indoor landmark positioning techniques. We believe that this review provides useful viewpoints and necessary information regarding indoor positioning technology using landmarks.