Instrumentation
- Satellite image of Chlorophyll a, August 2002.
Sensor networks, consisting potentially of a very large number of diverse sensors interconnected via a low data-rate communication network, are considered by international funding agencies such as the European Commission, DARPA, and NSF to be one of the top five emerging technologies to impact on the quality of human life over the next 20 years. The term ‘sensor network’ refers to an array of small, wirelessly interconnected sensors that collectively stream sense data to a central data aggregation point. Some sensors can be set to sample according to trigger conditions (e.g. monitoring salinity more frequently after rainfall) but since communications with the sensors will be bi-directional they can also be manipulated by central land-based control systems.
- Davies communications platform
This initial activity will deploy sensor networks on locations on the Great Barrier Reef (GBR) to collect real-time data at spatial and temporal scales required to understand complex marine processes, particularly those involving the interface between pelagic and benthic environments. Data from a local network will be aggregated and streamed in real-time back to a staging data centre onshore (GBR Node Data Centre) where they will be quality assured and processed for submission to the eMII as conformal data.
Deployed Equipment
The typical deployment of a Sensor Network at a reef consists of a Base Station that transmits the data back to the mainland and which interfaces the back-haul network to the on-reef network.
A series of network relay poles are then deployed around the reef to create the on-reef wireless network using 850MHz Spread-Spectrum radio. The poles form an ad-hoc network and are set up to transmit data from any device that is present in the range of the pole. Typically poles are located at two kilometer distance in shallow sandy locations. Poles are able to support a range of sensors as well and are used to mount the weather stations.
Two designs of buoys are then deployed into the wireless network, normally these are moored but as they have a GPS unit it is possible for this to be configured as drifters. The smaller buoy is 1350mm in diameter and is called a Senor-Float, it is suitable for shallow protected deployments. A larger 1750mm Multi-Float is used where the depth is greater than 12m or where waves and currents are stronger. The larger buoy is better able to remain steady in areas of stronger waves and currents.
For details of the equipment click on the links below: