to ground the technical discussions for the rest of the age distance from a sensor to the signal source, hence book. improving the signal-to-noise ratio (SNR). Let us consider the acoustic sensing case in a two-dimensional plane, where the acoustic power received at a distance r is 3.7.3.1 Habitat monitoring: Wildlife Preceive & Psource conservation through autonomous, nonintrusive sensing which assumes an inverse distance squared attenuation. On a small patch of land 10 miles off the coast of Maine, The SNR is given by a team of computer engineers from the University of California, Berkeley, are conducting an experiment in SNR, 10 log Precium networked sensing. Working with biologists at the College of the Atlantic, the engineers have installed 190 - 10 logr. wireless sensors that are being used to monitor the habitat of the nesting petrels 1 on Great Duck Island (see Increasing the sensor density by a factor of k reduces the Figure 3.7-4). In the past, biologists studying the nesting average distance to a target by a factor of 1/2 Thus, the behaviors of these birds had to travel to the island every SNR advantage of the denser sensor network is now and then to gather observation data. To check on the 1 This is the name given to various ocean birds belonging to the order of tube-nosed swimmers, like the albatross and the shearwater. CHAPTER 3.7 Wireless sensor networks Light Node . Temperature Thermopile (Passive infrared) Relative Humidity Figure 3.7-4 Remote wireless sensors are used to find out more about birds in their natural habitat. (a) Sensor network deployment Great Duck Island, 10 miles off the coast of Maine, (b) Wireless biological sensors placed in bird nests, (c) A petrel, rarely birdwatchers. (d) Sensor measurements remotely retrieved using a Web interface, summer 2002. (Picture courtesy of U.S. Geological Survey, Intel Corporation, and John Anderson). petrels, they literally had to stick their hands into the experience, thanks to the Internet. The untethered, burrows, often causing the birds to ab