18.3.2 Content Interoperability Standards
The content interoperability can be enabled by using common encoding standards.
The suite of ISO standards includes ISO 19115-metadata (ISO 2014a), ISO 19115-2imagery metadata (ISO 2009), ISO 19119-service (ISO 2016), ISO 19130 (ISO
2010), ISO 19130-2-sensor model (ISO 2014b), and ISO 19158-quality (ISO 2012).
The feature data can be described by Geography Markup Language (GML) (Cox
et al. 2002) and Keyhole Markup Language (KML) (Wilson 2008) (Cox 2006). The
raster data can be described by Hierarchical Data Format-Earth Observing System
(HDF-EOS). The sensors and observations can be described by Observations and
Measurements (O&M) (Cox 2006) and SensorML (Botts and Robin 2007).
18.4 Geospatial Web Service Architecture for Agriculture
18.4.1 A Specific Example: CropScape
CropScape, which is funded by USDA NASS, is a Web service–based application
for exploring and disseminating US conterminous geospatial cropland data products
for decision support. CropScape provides useful functions of online visualization,
geospatial navigation and querying, delineation of the area of interest (AOI), on-thefly data analysis and download, and thematic map creation.
Figure 18.3 shows the general service architecture of CropScape. A three-layer
framework is adopted to share and distribute geospatial data for agriculture (Han
et al. 2014b). OGC geospatial data and service standards are adopted to make this
framework interoperable, extensible, and reusable. W3C standards are also adopted
in the implementation of geospatial processing services. Apache Tomcat and Axis2
were used as the runtime environment for OGC WPS service and Web services for
its efficient, modular, configurable, and secured framework. MapServer was used to
serve the geospatial raster and vector data from OGC WMS, WCS, and WFS service
for its high performance and robustness. Geospatial Data Abstraction Library
(GDAL) (OSGeo 2011) and Two-dimensional Graphic Library (Cairo) (Cairo
2011) were utilized to develop executable programs.
18.4.1.1 Application Layer
The application layer includes various geospatial applications that support standardized Web services, OGC Web services, and workflows. CropScape could configure
the WMS, WCS, WFS, and WPS services to support geospatial data retrieval,
processing, and rendering in an interoperable manner. Other applications like
Geobrain (Di 2004) and ArcGIS Explorer (ArcGIS 2017) could mash up available
online data services with local data layers or invoke Web processing services in their
394
L. Hu et al.
The content interoperability can be enabled by using common encoding standards.
The suite of ISO standards includes ISO 19115-metadata (ISO 2014a), ISO 19115-2imagery metadata (ISO 2009), ISO 19119-service (ISO 2016), ISO 19130 (ISO
2010), ISO 19130-2-sensor model (ISO 2014b), and ISO 19158-quality (ISO 2012).
The feature data can be described by Geography Markup Language (GML) (Cox
et al. 2002) and Keyhole Markup Language (KML) (Wilson 2008) (Cox 2006). The
raster data can be described by Hierarchical Data Format-Earth Observing System
(HDF-EOS). The sensors and observations can be described by Observations and
Measurements (O&M) (Cox 2006) and SensorML (Botts and Robin 2007).
18.4 Geospatial Web Service Architecture for Agriculture
18.4.1 A Specific Example: CropScape
CropScape, which is funded by USDA NASS, is a Web service–based application
for exploring and disseminating US conterminous geospatial cropland data products
for decision support. CropScape provides useful functions of online visualization,
geospatial navigation and querying, delineation of the area of interest (AOI), on-thefly data analysis and download, and thematic map creation.
Figure 18.3 shows the general service architecture of CropScape. A three-layer
framework is adopted to share and distribute geospatial data for agriculture (Han
et al. 2014b). OGC geospatial data and service standards are adopted to make this
framework interoperable, extensible, and reusable. W3C standards are also adopted
in the implementation of geospatial processing services. Apache Tomcat and Axis2
were used as the runtime environment for OGC WPS service and Web services for
its efficient, modular, configurable, and secured framework. MapServer was used to
serve the geospatial raster and vector data from OGC WMS, WCS, and WFS service
for its high performance and robustness. Geospatial Data Abstraction Library
(GDAL) (OSGeo 2011) and Two-dimensional Graphic Library (Cairo) (Cairo
2011) were utilized to develop executable programs.
18.4.1.1 Application Layer
The application layer includes various geospatial applications that support standardized Web services, OGC Web services, and workflows. CropScape could configure
the WMS, WCS, WFS, and WPS services to support geospatial data retrieval,
processing, and rendering in an interoperable manner. Other applications like
Geobrain (Di 2004) and ArcGIS Explorer (ArcGIS 2017) could mash up available
online data services with local data layers or invoke Web processing services in their
394
L. Hu et al.