Effects of coordinate system and position of AR notification while walking

Augmented reality (AR) head-mounted displays (HMDs) allow users to easily receive notifications while participating other tasks by projecting information directly in their field of view. Although HMDs offer such benefits in displaying notifications, there is insufficient research on the effective placement of AR notifications when the user is walking. For this, we conducted two studies based on different types of AR information to identify how the users perceive and understand the AR notifications according to placement while walking. We compared two different coordinate systems (display-fixed and body-fixed) and three different positions (top, right, and bottom) for icon-type and text-type notifications. The results indicated that using a display-fixed coordinate system for icon-type notifications yields significantly higher noticeability and comprehension. In contrast, using a body-fixed coordinate system for text-type notifications significantly improved comprehension and walking performance. Regarding the position of notifications, the bottom position resulted in a significantly higher noticeability and comprehension for both icon- and text-type notifications compared with the top. Based on these results, we draw some recommendations for the future design of notifications in AR HMDs.