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People often ask, Where are you? in daily conversations. Knowing friends´ locations is for social connections, social gathering, accountability, and self-presentation. There are many location-sharing services (LSS) for the above purposes. The public, however, has trouble with the existing LSS, regarding privacy, mixed relationships, social pressure, unwanted attention, and hiding one´s location from friends. These concerns stop them from using LSS. In order to eliminate these concerns, we propose Longitude. (1) For privacy, Longitude users only share snapshots of their locations when their friends request. All location requests are recorded in Longitude Log. (2) For mixed social relationships, the users only share their specific locations with a strong tie. Longitude uses the contact frequency to decide whether a friend is a strong tie or weak tie. (3) For attention management, the users can broadcast their locations based on how much attention they want. (4) For hiding from friends, the users can have a safe excuse to do it. Our design provides the implications for future LSS development. Until people are free of concerns, they would not start using LSS on a daily basis.

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Chung-Yi Cho obtained his Master´s degree in Information and Computer Science at University of California, Irvine and his Bachelor degree in Computer Science at Soochow University, Taiwan. He is currently a software engineer in Austin, Texas and can be found travel around with his camera.

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