smart sensors and the environment

Box 2 | Intelligent sensor networks

What's so special about an intelligent sensor network? Isn't it just a series of sensors recording their surrounding environment? Actually, intelligent sensor networks are a lot more and the key word is 'network'. Each sensor is a node in a larger interconnected network, and that network has properties that enhance the value of the information being collected from any individual sensor. The whole (the network) is more than the sum of its parts (the data collected by an individual sensor).

Each sensor node has the ability to collect a variety of environmental data, process that information and communicate it to other sensor nodes in the network. That makes the nodes pretty clever, but when they're working together the network they form has its own special abilities. The data being collected from all the sensors can be sent back to 'headquarters' from a single node, rather than using multiple streams of data. This reduces band width requirements as well as power consumption for the communication of the network's information.

In addition, the fact that the network is passing on information from a number of sensors improves the accuracy of the information gathered compared to that obtained from a single sensor.

Sensor networks can also spot and deal with anomalous information from individual sensors – that is, information that isn't consistent with information coming from other nodes. It could be that the sensor delivering the unusual data has malfunctioned, as is often the case when a sensor is operating in a hostile environment such as the ocean. These so-called ad hoc networks can isolate faulty sensors and continue to provide quality information from the remaining sensors while, at the same time, signalling that the malfunctioning sensor needs attention.

However, it might be that the anomalous readings are the first sign of some type of environmental event taking place. For example, the signal might be the first appearance of colder or warmer water over a coral reef. If neighbouring sensors verify this 'event' then the network may be programmed to increase the monitoring capacity of the affected sensors (for example, double the number of temperature recordings being made). The network is sensitive to changes in environmental conditions and responds to ensure important information is captured – it has the capacity to self organise in response to a changing environment. Australian research is refining the technology for detecting unusual readings in sensor networks through the Great Barrier Reef Project.

The intelligent network can tell you what's happening at a variety of scales simultaneously. It can report back on changes happening around individual nodes but it can also interpret data from a cluster of nodes to demonstrate if some impact is happening at a larger scale.

So an intelligent network of sensors offers many advantages including variable network scales, reliability, efficient use of resources and lower power consumption.

Box
Box 1. Environmental applications of smart sensors

Related sites
Ad hoc networking in the forest (National Science Foundation, USA)
Ad hoc Networks (HowStuffWorks, USA)
March of the motes (New Scientist, 23 August 2003)

External sites are not endorsed by the Australian Academy of Science.
Posted December 2008.