Sensor net deployed in flood warning study

Researchers in the United Kingdom are deploying a trial network of wireless sensors intended to help predict river flooding.

Two of 13 sensor nodes have been installed on a section of the River Ribble in the Yorkshire Dales , northeast of Manchester. Eleven more will be deployed over the next few weeks, covering a kilometer of the waterway which regularly floods after Christmas.

One key difference with the project is that each fist-sized node has a built-in computer that measures water pressure and speed, in addition to a Bluetooth or 802.11b wireless radio and one or another type of physical sensors. As a result, the sensors will be able to coordinate data collection and processing, as if it were a larger distributed computer. Results, as well as the raw data, can be sent wirelessly over a cellular GPRS connection to a larger computation grid which can store the data and run compute-intensive models and simulations.

The project was reported in NewScientist.com on Oct. 23.

The nodes are powered by a combination of solar panels and batteries. Distances between them vary up to "tens of metres," perhaps up to 200 to 300 feet. Eleven nodes will measure water pressure in order to monitor the depth of the river. Two nodes, using different techniques, will measure the speed of the water: one via underwater ultrasound, the other from the shore, calculating speed by using a Webcam to track objects and ripples on the surface.

The nodes will be able to detect the river's changing behavior, and run the data through computer models to predict what may happen next.

In the future, the data, alerts, and predictions can be fed directly to local officials and emergency staff, and even to residents along the river bank by means of Web sites, e-mails, and sending SMS text messages to cell phone subscribers in the affected areas.

The technology has been crafted by a group of researcher at the University of Lancaster ( PDF ). Compute power is provided by the Gumstix platform , so-called because the motherboard system is about the size of a stick of chewing gum. Each stick has an Intel XScale CPU running at up to 400 MHz and offering 64MB of RAM and 16MB of flash memory. Each stick also includes a Bluetooth radio. For a few of the nodes, the researchers have added an 802.11b interface via a Compact Flash card.

The computer power comes at the price of electrical power: each Gumstix can draw 1 watt of power, up to a maximum of 3 watts. According to the researchers, the combination of a midsize solar panel and high-capacity battery can meet those power demands.

The Lancaster researchers created a component-based development framework, called GridKit, for building embedded applications as independent sets of components for the embedded computer network.

The nodes typically can share data through a multi-hop Bluetooth mesh. The 802.11b connections take over in the case of a Bluetooth radio failure, or to distribute larger data sets or images over the net.

A somewhat similar project, called FloodNet , has been underway in southern England, along the River Crouch, a tidal river in Essex. Floodnet was deployed in early 2004, with six wireless nodes equipped with pressure sensors. Changes in pressure are used to estimate the river's changing depth.

FloodNet nodes run the client of IBM's Websphere MQ messaging software, and are linked via 802.11b radios to a GPRS gateway that enables the sensor net to pass data to a server hosting IBM MQ Message Broker. MQ transcodes the data and makes it available to any application subscribing to the broker, such as simulations, visualization programs, and database services.