Mobile devices, such as smartphones and other personal devices, are increasingly used to view maps and other large datasets. Their necessarily small displays can only show a small portion of the data at one time. Researchers have developed various visual techniques that overlay icons or shapes onto the edge of the display to provide the user with hints regarding the existence and location of undisplayed points of interest. However, current techniques fail in practice on mobile devices because they are confusing, do not scale or take up too much valuable screen space.

In this thesis, I describe a new technique to visualize the location of off-screen points of interest. This technique, called Wedge, addresses specific shortcomings of existing techniques. This thesis details the design and implementation of Wedge and summarizes the results of a thorough experimental evaluation. Furthermore, I present a preliminary model of user performance that I use to highlight design suggestions for practitioners using Wedge.