Location-awareness is crucial to many applications of sensor networks. Existing location surveying approaches either rely on an inflexible infrastructure or suffer from high computation and communication load. In this paper, we present Non-intEractive lOcation Surveying (NEOS) to address certain deficiencies in the existing approaches. The key contribution of NEOS is twofold: (i) it employs a mobile beacon to introduce mobility-differentiated time-of-arrival (MDToA) observations, a special form of time difference of arrival (TDoA), at the node side and (ii) it involves simple computations and entails no node-to-node communication. MDToA enables us to devise flexible and robust positioning algorithms; the resulting computational load fully obeys the processing constraints of sensor nodes. Furthermore, the non-interactive feature of NEOS allows of a substantial reduction on the nodes energy consumption. We have implemented a preliminary prototype of NEOS using CricketMotes. Our experiments with this prototype demonstrate a location accuracy within 2cm in a 16m^2 area.