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Working Group 3. Architecture
Spiral 3 has four major components; primitive geospatial analysis functions, processing of the primitive geospatial analysis functions, model-builder and management of the model
builder. Among the four components, Spiral 3 focused on developing primitive geospatial analysis functions and its processing. In current, the model-builder and its management were
excluded from the development scope of Spiral 3. As alternative solutions, there are WPS Model Builder and WPS Request Builder of GeoServer for chaining one of geospatial analysis
functions.
The system development environment was determined as Java using GeoTools for the compatibility and portability. In Figure 1, a library of geospatial analysis functions (①) was
developed by using Java and GeoTools library. It is required that java compatible processing application environment to execute the geospatial analysis functions, to handle parameters,
to import/export of input datasets and so on.
For processing the library of geospatial analysis functions through Internet, OGC WPS extension should be developed. So the WPS extension of GeoServer (②) was developed by Spiral
3. For processing it on a desktop environment, a processing toolbox need to be developed. In Spiral 3, the processing toolbox was developed as a plug-in (③) of uDig SW which is a
Java-based open source desktop GIS. It means that the preparation and pre-processing of data for geo-analysis and the visualization of the analysis are supported by uDig.
For processing the library of geospatial analysis functions on Spiral 1 (④) of UN Open GIS platforms which is a geoportal service, a processing toolbox or an extension should be
developed. However, the Spiral 1 is not compatible with Java language, the fully-integrated development was excluded from the scope of Spiral 3 development.
Figure 1. Key components of Spiral 3 development
Implementation
Development of around 140 primitive geospatial analysis functions was done by Spiral 3. Parts of the analysis functions in comparison among GIS SWs are presented in Figure 1. Each function in the library (① in Figure 1) is executable by plug-in the library to uDig SW. All of the primitive functions will be shown up on the Processing toolbox of uDIG in Figure 3.
Figure 2. Comparison parts of geospatial analysis functions among GIS SWs
Figure 3. Geo-analysis functions of Spiral 3 on uDig SW
WPS Extension of GeoServer is available to download and use. When the WPS Extension is installed successfully, the WPS will be shown up on a list of service capabilities of Welcome page of GeoServer in Figure 4. All of Spiral 3 geospatial analysis functions can be checked through WPS request builder menu of GeoServer in Figure 5.
Figure 4. GeoServer WPS extension installed
Figure 5. Spiral 3 geospatial analysis functions on GeoServer
Assessment of the implementations
Geospatial analysis functions of Spiral 3 implemented open standards or open algorithms published as well as ArcGIS documents. The correctness of each geospatial analysis function of Spiral 3 was verified empirically. Some of functions were verified in comparison with ones of other SW like ArcGIS.
Although the name of functions is equal, the results of geospatial analysis functions are often inequivalent depending on algorithms or parameters implemented. For instance, the results from Quadratic function of ArcGIS and one of Spiral 3’s are different in Figure 6. So it does not mean that either one is wrong even though the results of the two functions are different.
Figure 6. Quadratic Comparison: ArcGIS (left), Spiral 3 (right)