Today, service innovation is just as important as product innovation. The ideation of service innovation, vis-à-vis product innovation, is user-oriented, rather than maker-oriented. Thus, capturing and understanding user context is key to being able to offer personalized and relevant services, and further identify new service opportunities. Therefore, a user-centric approach is needed in new service development, especially in the era of ubiquitous service. There exists a rich literature on how to incorporate customers into new service development, but most has focused only on their expressed needs, and failed to identify potential needs. In response, this paper proposes a 'user-centric service map', which first visualizes the portfolio of existing services based on the dictionary of potential needs and then helps to investigate vacuums that can provide a concrete shape for new service opportunities. The suggested approach is composed of three parts: first, constructing a potential needs dictionary, second, developing a service map, and finally, identifying new service opportunities. A case study of Apple's App Store services is conducted to verify the feasibility and utility of the proposed approach and offer strategic implications.