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Location information improves the routing effectiveness and facilitates the development of diverse novel applications in mobile networking. While they can lead to better user experiences, given privacy concerns and hardware constraints, a mobile user often exposes a limited number of locations only. We are thus interested in the Trajectory Exposure Problem in this context, i.e., to what degree that the user's trajectory (i.e., its route) is exposed? Furthermore, can the user adaptively control the exposure of its trajectory and yet offer useful information for location-based services? In this paper, we explore Gaussian Process Regression, an effective tool to re-construct the trajectory of the mobile user with selected exposed locations. We examine how the re-constructed trajectory differs from the real trajectory, i.e., evaluating the exposure rate. We present an effective heuristic that adaptively controls the trajectory exposure rate by carefully choosing the exposed locations. We further demonstrate a practical routing protocol, MoRPTE, which, controlled by a single parameter, utilizes location information flexibly and adaptively in the spectrum from zero knowledge to full knowledge to fit the applications' demands.