International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B4, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
SENSOR WEB SERVICES FOR EARLY FLOOD WARNINGS
BASED ON SOIL MOISTURE PROFILES
Thomas Brinkhoff^ *, Stephan Jansen b
? Jade University Oldenburg, Institute for Applied Photogrammetry and Geoinformatics, 26121 Oldenburg, Germany -
thomas.brinkhoff@jade-hs.de
b OFFIS Institute for Information Technology, 26121 Oldenburg, Germany - stephan jansen@offis.de
Commission IV, WG IV/2
KEY WORDS: Sensor, Monitoring, Floods, Environment, Internet/Web, Services, Interoperability, Visualization
ABSTRACT:
As result of improved computing and communication capabilities, the use of sensors and sensor networks for environmental
monitoring has gained considerable importance in the recent years. For an interoperable integration of sensor data like sensor
descriptions, sensor measurements and alarm events, the Open Geospatial Consortium (OGC) started the Sensor Web Enablement
(SWE) initiative and proposed several specifications in respect to a geospatial sensor web. First implementations of SWE software
frameworks are available. In this paper, we present the results of the recent WEBBOS project. Its objective was to build up a system
for early flood warnings by measuring soil moisture profiles. The use of soil moisture profiles is motivated by the fact that
traditional approaches like the observation of water gauges are suitable for the prediction of large-river flooding but not for smaller
drainage areas. We describe the architecture of our system and how it is built up by using existing software components to a large
extent. Our special focus is on the incorporation of 3D soil moisture profiles into the SWE data model, on the integration of the new
OGC Sensor Event Service, and on the development of a flexible web client for mapping and other visualization purposes.
1. INTRODUCTION
Recent disastrous floodings have demonstrated the demand for
early flood warnings. This need will be enforced by the
expected climate change that probably leads to more torrential
rain. In general, flood forecasts concentrate on large rivers
considering water gauges. However, there exist a large number
of smaller drainage areas ‘with a size of 100 to 1000 square
kilometers. In such areas, disastrous drainages may happen after
heavy rain that cannot reasonably be observed by gauges
because the water level changes very fast what prevents
warnings to be made in time.
Thus, the creation of early flood warnings for small drainage
areas is still an unsolved challenge. One promising approach for
solving this problem is the observation of the soil humidity
because that measure decides how much of the precipitation
will drain off. WEBBOS is a joint project of the Mannheim
University of Applied Sciences and the Oldenburg University
of Applied Sciences funded by the German Federal Ministry of
Education and Research. It has the objective to build a web-
based sensor system for early flood warnings by measuring soil
moisture profiles. Within this project, special sensors measuring
the soil humidity in different depths have been developed and
successfully tested. These sensors were integrated into sensor
nodes that form local sensor networks. Such a sensor network
should be located in an area with a high variety of soil
humidity.
Like in other early-warning and disaster management systems,
it is important to incorporate the sensor measurements into a
geospatial information service that allows managing sensor
data. This encloses the visualization of the sensor measurements
* Corresponding author.
and the control of the soil humidity sensors as well as the
detection and processing of alarm events. Interoperability is an
important issue for such systems. Therefore, the Open
Geospatial Consortium (OGC) started the Sensor Web
Enablement (SWE) initiative some years ago and specified
several services and data models in the meantime (Botts et al,
2006).
WEBBOS implemented its information system using those
specifications and a popular open-source SWE framework.
Many standard requirements can be solved by such an approach
without additional efforts. However, often there are important
demands that need more sophisticated solutions. Those cases
and their solutions for the WEBBOS project will be discussed
in this paper. One important aspect is that the use of soil
moisture profiles requires temporal 3D measurements and 3D
models of soil humidity for each sensor network: Only the
relation and difference between the humidity in different depths
and their development over the time allow detecting relevant
events. The temporal aspect is sufficiently covered by the
current SWE specifications. However, these specifications and
their implementation are mainly 2D-oriented.
Another important issue for early-warning and disaster
management systems is the detection of potentially dangerous
situations. This requires the description and detection of spatio-
temporal events. For this purpose, the OCG recently proposed
the Sensor Event Service (SES) (Echterhoff & Everding, 2008)
together with the Event Pattern Markup Language (EML)
(Everding & Echterhoff, 2008). Until now, only few
applications of the SES exist. Thus, the experience is limited.
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