News Release

A 19-year-old Johns Hopkins University sophomore physics major and resident of Wayne, Pa. is playing an important role in helping to develop a wireless monitoring system that may eventually assist earth scientists in developing a more detailed understanding of various ecosystems.

Joshua Cogan's research, which focused on whether an inexpensive, commercially available sensor called the Watermark is suitable for long-term soil monitoring use, was funded with the support of a Johns Hopkins Provost's Undergraduate Research Award. As one of about 40 PURA winners this academic year, Cogan presented his research at an awards ceremony which was held at Johns Hopkins on March 16.

Josh Cogan is part of an interdisciplinary team working on wireless sensor networks for monitoring soil in various city sites. Behind him are team members Razvan Masaloiu-E and Andreas Terzis and Cogan's faculty sponsor, Katalin Szlavecz. Photo by Will Kirk

Since 1993, about 40 students each year have received PURA grants of up to $3,000 to conduct original research; results from some projects have been published in professional journals. The awards, funded through donations from the Hodson Trust, are an important part of the university's commitment to undergraduate research.

Cogan got involved in earth science-centered research after taking an ecology course with Katalin Szlavecz, a senior lecturer in the Department of Earth and Planetary Sciences, during his freshman year. Impressed with Cogan's intelligence and acumen, Szlavecz recruited the physics major to work with her.

"It was almost immediately apparent to me that Josh would be an asset in my lab," said Szlavecz, who served at Cogan's PURA advisor. "He is very smart, and I knew that his background in physics and electronics would be an asset in our research and problem-solving."

Cogan joined an interdisciplinary team working on wireless sensor networks. The ultimate goal of the project is to develop a wireless soil monitoring system that can be installed in various sites (such as Leakin Park or Cub Hill) as part of the Baltimore Ecosystem Project, a long- term ecological research project focusing on urban environments. In addition to Szlavecz, the team includes Andreas Terzis, an assistant professor of computer science from the Whiting School of Engineering, computer science students Razvan Musaloiu-E and Sam Small, and Alex Szalay, a professor in the Henry A. Rowland Department of Physics and Astronomy.

"Soil monitoring systems collect data about the physical, chemical and biological attributes of soil in situ and almost constantly," Cogan explained. "Our goal is to develop a system at a scale that currently does not exist. Remote sensing networks allow us to collect data with minimal human intrusion, which is very important, because whenever humans go to the field to collect data, they inadvertently change the ecosystem they are measuring."

Cogan's role in the research involved assembling the sensors, which consist of electrodes embedded in a granular quartz material surrounded by a membrane and metal mesh, with a wire sticking out of the end. Cogan then soldered the wires to sensor boards, which had other sensors (to measure air temperature, soil temperature and light intensity) attached to them. He then attached those boards to a mote with a small antenna, which transmitted data about each sample to the lab's computer.

Over the course of the project, Cogan and the team learned that the Watermarks sensors were not adequately precise in measuring the data collected. They found that in order to get the level of precision they wanted, they would need to calibrate each sensor individually — a very time-intensive process.

"One of the lessons we learned here is that the Watermark sensor, though inexpensive, is not ideal for this kind of long-term monitoring," Szlavecz said. "But what we learned will also help us to improve our approach next time, both in hardware and in software."

Cogan learned valuable lessons not just about earth science, but also about interdisciplinary teamwork.

"You hear about interdisciplinary research all the time, but no one tells you how hard it is to simply communicate with all the different parties involved," he reflected. "Our computer science members speak about sampling, and transmission. The physicists — including me — talk about voltages and dielectric constants. The soil ecologists had other concerns, such as how soil invertebrate heterogeneity relates to physical factors in the soil. Believe me: communication was no trivial concern!"