Abstract
This study presents the latest updates to the Audubon Society of Western Pennsylvania (ASWP) testbed, a $50,000 USD, 104-node outdoor multi-hop wireless sensor network (WSN). The network collects environmental data from over 240 sensors, including the EC-5, MPS-1 and MPS-2 soil moisture and soil water potential sensors and self-made sap flow sensors, across a heterogeneous deployment comprised of MICAz, IRIS and TelosB wireless motes. A low-cost sensor board and software driver was developed for communicating with the analog and digital sensors. Innovative techniques (e.g., balanced energy efficient routing and heterogeneous over-the-air mote reprogramming) maintained high success rates (>96%) and enabled effective software updating, throughout the large-scale heterogeneous WSN. The edaphic properties monitored by the network showed strong agreement with data logger measurements and were fitted to pedotransfer functions for estimating local soil hydraulic properties. Furthermore, sap flow measurements, scaled to tree stand transpiration, were found to be at or below potential evapotranspiration estimates. While outdoor WSNs still present numerous challenges, the ASWP testbed proves to be an effective and (relatively) low-cost environmental monitoring solution and represents a step towards developing a platform for monitoring and quantifying statistically relevant environmental parameters from large-scale network deployments.
Highlights
The sustainable condition of our freshwater resources partially depends on our understanding of the natural system in which it is cycled [1]
The environmental data collected with the wireless sensor network (WSN) nodes were found to be similar to the data collected from the Decagon Devices Em50 data logger in terms of quality
The data readings from the WSN nodes are automatically collected and stored in a relational database system, all the environmental data are saved in a unified and integrated repository, eliminating the need to manually download data at each location
Summary
The sustainable condition of our freshwater resources partially depends on our understanding of the natural system in which it is cycled [1]. It has long been known that physically-based distributed hydrologic models require an understanding of the spatiotemporal variability of environmental data, which is difficult without an abundance of ground-based measurements for calibration and validation [2]. Sensors 2017, 17, 636 parameters on regional hydrologic and climatologic conditions need permanent in situ measurements. Ground-based measurements and monitoring of environmental variables have been impacted over the past decade by wireless sensor network (WSN) technology. Because of the high expense of sensors and data logging equipment, researchers are often forced to either forgo data loggers for high spatial density measurements with poor temporal resolutions (i.e., hand measurements) or obtain high temporal resolution at a limited number of strategically located data loggers
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