Localization in Multi-Modal Sensor Networks

We describe the design and implementation of solutions for localization problems in multi-modal wireless sensor networks. The problem of network self-localization, namely determining the positions of the nodes that comprise the network, is addressed optically using a set of pan-tilt-zoom (PTZ) cameras to search for a small light-source attached to each of the sensor nodes. Once the locations and headings of the network´s nodes are estimated by the cameras, the network can be used to detect and estimate the location of objects traveling through it. Target localization is performed within the network, using information from magnetometers connected to the sensor nodes. We evaluate the performance of the proposed target localization algorithms through simulations and an implementation running on MicaZ motes. Simulation results show that the localization error for a 100-node network whose nodes are randomly deployed over an area of 100 x 100 m, can be less than 10 cm. Moreover, our initial implementation results show that the median of the localization error for magnetic targets in a 1m x 1m field is 7.1 cm.