May 30, 2005
Engineering students develop a coral reef
By Françoise Chanut
Five senior engineering students at UCSC are trying to push
the limits of low-power wireless transmission to facilitate
the monitoring of remote natural environments.
The SEA-LABS team includes senior engineering students (left
to right) Jo Chou, Mike Maroney, Matt Bromage, Lee Wells,
and Chris Chan.
Photo: Tim Stephens
The apparatus they are building will track conditions on coral
reefs in distant locations and beam information back in real
time to a land-based station.
The students named their creation SEA-LABS, short for "Sensor
Exploration Apparatus utilizing Low-power Aquatic Broadcasting
SEA-LABS was originally designed to help UCSC biologist Donald
Potts track environmental changes that affect the reefs of Midway,
a remote atoll of the Hawaiian archipelago. But SEA-LABS also
has the potential to become a low-cost tsunami-warning device,
said Matt Bromage, a computer engineering student who acts as
SEA-LABS team manager.
According to Potts, a professor of ecology and evolutionary
biology, SEA-LABS should be a vast improvement over current
satellite imaging technology, which provides low-resolution
data at high cost. A typical satellite survey will provide average
temperatures of the ocean surface over areas up to 60 square
miles, he said.
"But the corals living on a reef may experience temperatures
that are 5 to 10 degrees different from that average. With SEA-LABS,
we will have miniaturized instrumentation that we can place
right where the corals and other animals and plants actually
live," Potts said.
The project began with a serendipitous encounter between Potts
and Katia Obraczka, an associate professor of computer engineering
whose research includes wireless sensor networks. Together they
hatched the idea of a collaboration, which Obraczka proposed
as a student project for the senior engineering design class.
Bromage and four classmates--electrical engineering senior
Lee Wells and computer engineering seniors Chris Chan, Mike
Maroney, and Jo Chou--volunteered. The students said they were
attracted by the opportunity to build something that had practical
applications and would have an impact.
Now entering its final testing stages, the project should culminate
this summer with a trip to the Midway atoll, 1,200 miles northwest
of Honolulu, where the students will install and test their
waterproof and salt-resistant prototype.
Wireless data transmission is a big advantage of SEA-LABS over
other commonly used environmental sensors, Bromage said. "Currently,
the state of the art for remote monitoring is a sensor attached
to a data logger, but you need to go out and retrieve the logger
after a set amount of time," he said.
Data loggers collect and store data but do not transmit it.
SEA-LABS will send information in real time, first through a
wireless connection to a land station on Midway, then through
an Internet connection between Midway and the mainland. Ideally,
traveling the 2,800 miles between Santa Cruz and Midway to service
SEA-LABS would only be necessary once a year.
The core of SEA-LABS is a Programmable Ocean Device (POD),
which consists of a processor, a memory storage component, and
a battery that can last up to two years, all housed in a waterproof
casing about the size of a small wastebasket. The POD can be
bolted to the seafloor near a reef. It must be completely waterproof
at depths up to 60 feet and sturdy enough to withstand heavy
The POD has cable connections to sensors that independently
record pressure, light, salinity, and temperature. The sensors
are small enough to fit in any desired location on or within
a reef and can be placed right next to plants, corals, and other
The pressure sensors monitor wave patterns, tides, and overall
sea levels. Eventually, real-time recordings from these sensors
could be used to help detect a tsunami wave.
The POD connects to a receiver/transmitter attached to a surface
buoy. The transmitter broadcasts the data recorded by the sensors
from the POD to a base station on land via a radio antenna.
The challenge for this step is to find a good compromise between
signal strength and battery life, Obraczka said.
"You can always increase signal strength by increasing
power, but then the battery will run out sooner," she said.
On the other hand, if the signal from the POD is too low, the
land antenna might not be able to pick it up, which would result
in incomplete data collections. With an antenna 150 feet above
ground and transmitters on one-foot high buoys, SEA-LABS should
work within a five- to seven-mile range. That range should accommodate
the geography of the Midway reef, Potts said. But the final
tuning of SEA-LABS will only be possible at Midway.
"The problem is that wireless transmission is very sensitive
to the environment," Obraczka said.
The Midway atoll consists of three small islands surrounded
by a well-developed reef. A U.S. Navy base for over 50 years,
the atoll became a National Wildlife Refuge under the jurisdiction
of the Fish and Wildlife Service in 1996. Since then it has
suffered minimal human impact, which makes it a good place to
study ecological and evolutionary responses to changing natural
conditions, Potts said.
The health of a reef depends on complex interactions between
corals and algae, which themselves depend on water temperature,
depth, salinity, and acidity. Potts expects the environmental
impacts of global climate change to become detectable on Midway
and its reef in the near future, but predicting what will happen
"The physical environment is unpredictable and the climatic
conditions unstable," Potts said. "As climatic conditions
change, the patterns of winds, storms, currents, and upwellings
will change at a regional scale."
An important goal of the SEA-LABS team is to provide technology
that benefits users with small budgets, such as developing countries
or U.S. wildlife reserves with limited government or private
funding, Potts said. To this end, the students use off-the-shelf
components and develop nonproprietary open-access software.
Depending on the number of sensors attached to each POD, SEA-LABS
should cost between $500 and $1,000 per POD. Eventually, mass
production could lower the cost even further.
Though only two stations will be ready this summer, Potts would
eventually like to install 10 stations along the Midway reef.
According to Bromage, one of the best features of SEA-LABS is
the ability of the PODS to communicate with each other and establish
ad hoc networks. If a POD is too far from the base station,
it can transmit its information to a nearby POD, which will
relay it to another POD or to the base station.
The idea of the senior engineering design class is to mimic
an industry environment, said computer engineering lecturer
Stephen Petersen, who teaches the senior design class and advises
SEA-LABS on radio frequency. While the students sharpen their
engineering wits, they also learn to work as a team, a skill
that will serve them well in future job settings.
And what happens to SEA-LABS after this summer, when the class
"We're hoping to pass it on to the next class so they
can do something more sophisticated with it," Chan said.
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