Location-based systems (LBS) represent an emerging genre of applications that exploit positioning technologies and facilitate a wide range of location-based services. Unlike conventional information systems, LBS data management is challenging because LBS data is high dimensional and spatio-temporal in nature, and information leakage may result in location related privacy crises. The issue has become even more complicated, as database outsourcing has become inevitable in view of the emerging popularity of LBS deployment. In this paper, we tackle the research challenge and propose a SecUre Database Outsourcing system, called SUDO. By combining the techniques of Hilbert space-filling curves, different invertible encryption algorithms, and genuine mixed data, we show that SUDO is capable of preserving location privacy for LBS against different attacks. Moreover, the proposed solution is simple, effective, and scalable; and it shows promise in supporting LBS data management with outsourced databases. Copyright is held by the owner/author(s).