Wireless sensor networks are a promising technology for ecological research due to their capability to make continuous and in-situ measurements. However, there are challenges for the wide adoption of this technology by field ecologists. The observation system needs to be rapidly and easily deployable at remote locations, flexible to meet the requirements of different applications, and reconfigurable by scientists who may not be technology experts.
In this joint USC/ISI–UCLA/CENS deployment at Stunt Ranch in the Santa Monica Mountains, we are interested in a long-term investigation of the influence of the 2006-07 southern California drought conditions on the water relations of chaparral shrub and tree species that differ in their depth of rooting. Rainfall over this past hydrologic year in southern California was less than 25% of normal, making it the driest year on record. In addition to core measurements of air temperature, relative humidity, wind speed, solar irradiance, rainfall, and soil moisture, we use constant-heating sap flow sensors on replicated stems of selected species.
Results/Conclusions
Due to inconsistent cellular data coverage in this semi-remote location, we chose a commercial satellite service provider for a live Internet data link. We use a tiered architecture approach because of the distributed sensing requirements in our deployment. A suite of environmental sensors is connected to a Compact RIO, a rugged data acquisition platform from National Instruments, which is co-located with the satellite dish and the only location served by line power.
Sap flow sensors are deployed from 20 to 50 meters away from the Compact RIO. Additionally, Onset Hobo dataloggers are used to collect microclimatic data near the sap flow sensors. Crossbow motes interface with the sap flow sensors and the Hobo datalogger and send data to the Compact RIO through wireless communication, allowing the satellite link to be shared among various distributed sensor arrays.
The back-end system stores the data in a database and provides interfaces for easy data retrieval and system reconfiguration. Our unique data exchange and management protocols for reliable data transfer and storage, and our tools to support remote system monitoring and configuration allow near real-time monitoring of data.
This poster describes our deployment in detail, examines the various trade-offs in power, data acquisition, and communication technologies, and discusses our design, which has emphasized a modular software architecture that is flexible to support various scientific applications and has successfully collected data since its installation.