The work falling into the second category concentrated on research efforts to help cognitively impaired elders carry out daily outdoor routines safely, by providing simply navigation or anomalous event detection services based on users’ movement information. Spatial deviations of traveling trajectories were frequently explored in this field to tackle possible anomalies, such as taking an incorrect bus, that are usually faced by elders. One of the earliest works is the University of Washington’s Opportunity Knock system [15], which tracks a person’s movement and finds potentially erroneous behavior based on a transportation mode learned from users’ history. In addition, unsafe wandering behavior was also explored in our previous work [16], which is realized via detecting invalid movement patterns when elders travel alone in outdoor environments