In this paper, we present a distributed location discovery frame- work, called Sextant, that extracts geographic constraints fromalready- present wireless radios and uses these constraints to infer node and event location with high accuracy. Sextant operates by setting up a system of relative geographic constraints among the network par- ticipants based on network connectivity and solving this system in a distributed and efficient manner with the aid of absolute position information provided by a small number of landmarks. A landmark is a node whose absolute position is known; Sextant landmarks can be cheap static nodes whose positions are fixed, or they may be mo- bile nodes equipped with dedicated hardware,.
