In this paper we describe a prototype audio user interface for a Global Positioning System (GPS) that is designed to allow mobile computer users to carry out a location task while their eyes, hands or attention are otherwise engaged. Audio user interfaces for GPS have typically been designed to meet the needs of visually impaired users, and generally (though not exclusively) employ speechaudio. In contrast, our prototype system uses a simple form of non-speech, spatial audio. This paper analyses various candidate audio mappings of location and distance information. A variety of tasks, design considerations, technological opportunities and design trade-offs are considered.The findings from pilot evaluation experiments are reported. Finally, opportunities for improvements to the system and for future empirical testing are explored.

Abstract. Direct Combination (DC) is a recently introduced user interaction principle. The principle (previously applied to desktop computing) can greatly reduce the degree of search, time, and attention required to operate user interfaces. We argue that Direct Combination applies particularly aptly to mobile computing devices, given appropriate interaction techniques, examples of which are presented here. The reduction in search afforded to users can be applied to address several issues in mobile and ubiquitous user interaction including: limited feedback bandwidth; minimal attention situations; and the need for ad-hoc spontaneous interoperation and dynamic reconfiguration of multiple devices. When Direct Combination is extended and adapted to fit the demands of mobile and ubiquitous HCI, we refer to it as Ambient Combination (AC). Direct Combination allows the user to exploit objects in the environment to narrow down the range of interactions that need be considered (by system and user). When the DC technique of pairwise or n-fold combination is applicable, it can greatly lessen the demands on users for memorisation and interface navigation. Direct Combination also appears to offers a new way of applying context-aware information. In this paper, we present Direct Combination as applied ambiently through a series of interaction scenarios, using an implemented prototype system.