International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B-YF. Istanbul 2004
geoprocessing systems to communicate with each other using
XML and HTTP. This means that systems capable of working
with XML and HTTP will be able to both advertise and use
OGC Web Services. Among OGC Web Service standards,
Sensor Collection Service(OGC, 2003b) focuses mainly on the
interoperable interface requirements for sensors. Table 1 shows
the SCS interfaces provided by GeoSWIFT services.
Requests Responses
The responding XML of service’s
capabilities conforms OGC Service
Information Model Schema(OGC,
2003a), provides detailed information
for a client to access the service. The
GetCapabilities
provided information includes Service
Type, Service Instance, Content Type,
and Content Instance.
GetObservations The responding XML of
GetObservation request is encoded
conforming to GML and O&M
schema. It contains values, units and
of the
locations requesting sensor
observations.
The XML describes the
sensor platform, and conforms to
SensorML(OGC, 2002) schema. An
example of a sensor platform can be a
DescribePlatform response
plane which carries a camera, several
inertial and
sensors. The plane is the platform for
sensors meteorological
those sensors.
DescribeSensor The XML response contains detailed
information of sensor characteristics
encoded in SensorML. The sensor
characteristics can include lists and
definitions of observables supported by
the sensor.
Table 1. Web Service Interface provided by GeoSWIFT Server
2.2 GeoSWIFT System Architecture
We now describe GeoSWIFT’s system architecture,
functionality of individual components and how they operate
together. The purpose of GeoSWIFT is to build a small scale
sensor web which consists of heterogeneous sensors and to
develop an open geospatial sensing service for sensor
information fusion. Three different sensing resources, network
configurations and setting are implemented and tested in
GeoSWIFT. Figure 4. shows the system architecture of our
current implementation of GeoSWIFT.
83
GeoSWIFT
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Figure 4. GeoSWIFT System Architecture Diagram
2.2.1 | MICA2 Wireless Sensor Networks:
GeoSWIFT currently includes and has tested three sensing
resources with different capabilities and settings. The first
sensing resource of GeoSWIFT is a wireless sensor network.
As we set forth in the previous section, wireless sensor
networks give us new capabilities for sensing and collecting
data about an environment. In the future sensor web, large
amounts of wireless sensor network nodes will be embedded in
our daily lives and provide pervasive and intelligent sensing.
We set up a small scale wireless sensor network for this testbed
environment.
We are using MTS-310 sensor board (sensor layer) and MICA2
mote (network layer) acquired from Crossbow technology Inc.
as the sensor network nodes for GeoSWIFT(Figure 4). MTS-
310 sensor board has a light sensor, temperature sensor, a
microphone, a sounder, a tone detection circuit, a 2 axis
accelerometer, and a 2 axis magnetometer. MICA2 provides
the wireless communication capability (1000 feet maximum,
outdoor) limited processing power (a microcontroller runs
TinyOS), and considerable amount of nonvolatile storage (512
KB) for sensor board. The sensor board is plugged into a
MICA2 node and the size of a MICA2 with a sensor board is
approximately 2.0 x 1.5 x 0.5 inches.
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Figure 4. MICA2 motes deployed in GeoSWIFT
Communication between wireless sensor network and the
GeoSWIFT sensing server is transmitted through a gateway.
