In sensor networks, fine-grained
time synchronization and localization are needed to detect events of interest in
the environment under observation. Location needs to be tracked both in local
three-dimensional space (e.g., On what floor and in which quadrant is the smoke
detected? What is the temperature of the atmosphere at height h?) and over a
broader topography, to assess detection levels across a related set (array) of sensors
(e.g., What is the wind direction for wind containing contaminated particles at milepost i, i þ 1, i þ 2, etc., along a busy highway?). Localization is used for functionality such as beamforming for localization of target and events, geographical
forwarding, and geographical addressing [1.5].