Sensor Webs in Digital Earth: Monitoring Climate Change Impacts
Matt Heavner (Univ Alaska Southeast, Juneau, Alaska)
Rob Fatland (Vexcel/Microsoft Geospatial Solutions, Boulder, Colorado)
Eran Hood, Cathy Connor (Univ Alaska Southeast, Juneau, Alaska)
Tracy Lee Hansen, Mary Sue Schultz, Tom LeFavre
(NOAA Earth System Research Lab, Boulder, Colorado)
Albert Esterline (NCA&T, Greensboro, North Carolina)
ABSTRACT: The University of Alaska Southeast is currently implementing a sensor
web identified as the SouthEast Alaska MOnitoring Network for Science,
Telecommunications, Education, and Research (SEAMONSTER). From power systems
and instrumentation through data management, visualization, education, and public
outreach, SEAMONSTER is designed with modularity in mind. We are utilizing virtual
earth infrastructures to enhance both sensor web management and data access. We will
describe how the design philosophy of using open, modular components contributes to
the exploration of different virtual earth environments. We will also describe the sensor
web physical implementation and how the many components have corresponding virtual
earth representations. This presentation will provide an example of the integration of
sensor webs into a digital earth. We suggest that sensor networks and sensor
webs should integrate into digital earth systems and provide a resource easily accessible
to both scientists and the public.
The initial scientific application of the SEAMONSTER sensor web is to monitor climate
change impacts of glaciated watersheds in Southeast Alaska. Melting glaciers are
dominating the biogeochemistry of watersheds and as the glaciers disappear, this
influence will diminish. By monitoring these watersheds using a sensor web, we are
improving knowledge regarding impacts of climate change.
INTRODUCTION
Impacts of climate change are especially pronounced in the polar regions of the
planet (ACIA, 2005). Because these areas are less accessible to the majority of the
population, the regions are historically less well studied. Additionally, public awareness
of the impacts of climate change in the polar-regions is often lacking. One important
aspect of climate change impacts is on the cryosphere, or frozen water regions of the
world. By understanding the changes of glaciers in more equatorial regions of the poles,
we provide insight into the potential responses of the large masses of ice (e.g. Greenland,
Antarctica)
Deploying a large number of sensors or utilizing satellite remote sensing is the
present technology for environmental remote sensing over a large geographical region.
NASA and other groups are exploring the concept of a sensor web. A NASA Earth
Science Technology Office Advanced Information Systems Technology workshop on
Sensor Webs developed the definition:
“A sensor web is a coherent set of heterogeneous, loosely-coupled,
distributed nodes, interconnected by a communications fabric that can
collectively behave as a single dynamically adaptive and reconfigurable
observing system. The Nodes in a sensor web interoperate with common
standards and services. Sensor webs can be layered or linked together.”
(AIST, 2007)
The critical difference between a sensor web and a sensor network is the
communication and semi-autonomous operation (and reconfiguration) of the
heterogenous nodes. We report on the SEAMONSTER project which implements sensor
web technology in Southeast Alaska and provides a specific example of the difference
between a sensor network and a sensor web. The communication and reconfiguration
aspects of a sensor web are described in more detail by AIST (2007) and Delin (2005).
The University of Alaska Southeast campuses are located within the diverse
ecosystems of Juneau, Sitka, and Ketchikan. The campuses are contained within the 17
million acre Tongass National Forest, they border the Juneau Icefield that contains 38
major glaciers covering 1,500 square miles, and a glacial fjord system containing
thousands of islands.
The South East Alaska MOnitoring Network for Science, Telecommunications,
Education, and Research (SEAMONSTER) is a NASA-sponsored smart sensor web
project designed to support collaborative environmental science with near-real-time
recovery of large volumes of environmental data. Southeastern Alaska is a challenging
research environment because of access issues. Due to the mountainous terrain and the
island nature of southeast Alaska, access to research sites is unpredictable and expensive
and often a primary constraint to research. As a result, the development of a smart sensor
web in southeast Alaska will be of tremendous benefit to ongoing earth science and
ecological research by UAS and state and federal agency researchers. The UAS campus
has access to diverse environments with both inter-tidal ocean and glaciers within 10
kilometers of campus. The initial geographic focus is the Lemon Creek watershed near
Juneau Alaska with expansion planned for subsequent years up into the Juneau Icefield
and into the coastal marine environment of the Alexander Archipelago and the Tongass
National Forest.
The overarching concept of SEAMONSTER is that the first generation of sensor
web technologies currently exist. SEAMONSTER is an implementation of those
technologies intended to act as an educational tool, a public resource, a scientific
resource, and a sensor web testbed.
The Lemon Creek
watershed illustrated in the
adjacent
Figure
is
accessible from Juneau
while offering the extreme
conditions
found
in
Southeast Alaska. Microsensor clusters (motes) are
indicated as red dots and
Microserver (more capable
computer) nodes are orange
triangles in this example
installation. The Lemon
Creek
watershed
is
relatively compact (~31
square kilometers) and begins on Lemon Glacier with two supra-glacial lakes at its head.
These lakes have periodic outburst drainages that enter Lemon Creek proper via subglacial drainage channels. Below this glacier Lemon Creek flows through steep
wilderness terrain, fed by several tributaries, before reaching a region of active mining
and industrially zoned use, finally flowing past residential housing in Juneau and
emptying into the ocean.
UAS has been involved in monitoring the outburst activity of supra-glacial lakes
using in-situ pressure transducers with data-loggers. Instrumentation of the lakes, the
Lemon Glacier surface (to study any glacial surge or reaction to lake drainages, via
geophones and GPS observations), and throughout the watershed provide water quality
monitoring, meteorological parameter monitoring (for autonomous prediction of possible
drainage events and the resultant change in sensor-web state for enhanced data
acquisition), and hazard monitoring. The Lemon Creek watershed is be instrumented via
a sensor web to monitor turbidity, flow, temperature, and meteorological parameters.
The catastrophic drainage of the lakes and the resulting impact on the watershed is a
transient event that requires sensor web technology to provide autonomous adaptation to
current environmental conditions to correctly observe the impacts of the lake drainage on
the Lemon creek Watershed.
The sensor platforms of SEAMONSTER operate via battery banks and solar panel
recharging. The power constraint limits the sampling frequency and operation time of the
computers on the sensors. Therefore long sleep cycles are required for power
consumption. When a sudden lake drainage is detected (either by a sudden drop in the
pressure transducer readings in the lake, or a drastic change in the water temperature at
the terminus of the glacier), all platforms can receive the alert signal and increase the
sample rate to observe the lake drainage and associated watershed impacts.
A second SEAMONSTER study site is the Mendenhall Glacier. Changes in glacier
volume and extent are key indicators of climate change. The Mendenhall Glacier is
located 10 km northeast of the UAS campus. SEAMONSTER is used to monitor the
mass balance (and retreat) of Mendenhall Glacier in partnership with the US Forest
Service. The maintenance of a consistent mass balance program on the Mendenhall will
help fill an approximately 3,000 km gap in glacier monitoring along the Pacific Coast of
North America. The observations are communicated to the public using digital earth
technologies to increase public access.
Digital Earth is a phrase to describe the virtual 3-D representation of Earth that is
spatially referenced and hyperlinked. Examples include Google Earth, Microsoft Virtual
Earth, NASA Worldwind, and ESRI’s ArcGIS framework. The digital earth technologies
are presently rapidly evolving. Standards efforts by the Open Geospatial Consortium are
being implemented for the SEAMONSTER sensor web. This leverages the increasingly
available digital earth technology for sensor web management, data analysis, and
education and public outreach.
Using Digital Earth technology, scientific and public access to SEAMONSTER
observations of climate change is increased. Shown above is the retreat of the
Mendenhall Glacier during the 2007 summer. This information is given to the US Forest
Service Mendenhall Glacier Visitors Center and shared with the approximately 300,000
visitors. By sharing this information via the Internet, even more of the public can be
made aware of these observations. A second example of the use of digital earth and
sensor webs is the display of water quality parameters in Google Earth via kml. In the
Lemon Creek Watershed, this plot shows water temperature by color (4.5-9.0 C, seen in
legend on left). One can explore the drainage and see that the main channel is cooler
(light blue) and dominated by glacial melt. The non-glacial tributaries (orange, red,
yellow) are warmer before they join the main channel.
Additional education and public outreach activities include involving K-12
teachers participating in the NSF funded EDGE program (above) in understanding sensor
web applications for glacier research. Each teacher participating sends two K-12 students
to a summer UAS workshop. The students and teachers are able to maintain involvement
with the SEAMONSTER project through the digital earth files we distribute.
Finally, Lemon Glacier was studied as part of the 1957-58 International
Geophysical Year. Lemon Glacier studies during the 2007-8 International Polar Year are
creating a legacy of next generations scientists prepared for sensor web use.
ACKNOWLEDGMENTS
Funding for SEAMONSTER is provided through NASA Earth Science
Technology Office grant AIST-05-0105, NOAA Education Partnership Panel
Interdisciplinary Scientific Environmental Technology (ISET) Cooperative Science
Center Grant, and NSF Research Experience for Undergraduates Grant No. 0553000.
Logan Berner, Marijke Habermann, Erica Halford, Josh Jones, Edwin Knuth, Nick
Korzen, Holly Moeller, David Sauer, Shannon Siefert, Suzie Teerlink, Larry Brewster
and James Miller have provided SEAMONSTER support.
CONCLUSIONS
Sensor webs represent the next technological step in environmental monitoring of
both long-term climate trends and transient events. Incorporating sensor web and digital
earth technologies improves scientific studies, educational efforts, and public outreach all
associated with climate change.
REFERENCES
Arctic Climate Impact Assessment Scientific Report (ACIA), 2005, Cambridge
University Press.
Report from the Earth Science Technology Office (ESTO) Advanced Information
Systems Technology (AIST) Sensor Web Technology Meeting, February 13-14, 2007
http://esto.nasa.gov/sensorwebmeeting/files/AIST_Sensor_Web_Meeting_Report_2007.pdf
Delin, K.A. (2004). Sensor Webs in the Wild. In: N. Bulusu and S. Jha (eds.), “Wireless
Sensor Networks: A Systems Perspective,”, Artech House.