WPS
GRASS based OGC Web Processing Service (WPS) standard implementations
The OGC Web Processing Service (WPS) Web Processing Service interface standard provides rules for standardizing how inputs and outputs (requests and responses) for invoking geospatial processing services as a web service. GRASS GIS can be used as backend in several WPS service frameworks.
Inside GRASS 7
In GRASS7, the WPS process description can be automatically generated with the option '--wps-process-description'. See announcement.
Example:
r.grow --wps-process-description
<?xml version="1.0" encoding="UTF-8"?>
<wps:ProcessDescriptions xmlns:wps="http://www.opengis.net/wps/1.0.0"
xmlns:ows="http://www.opengis.net/ows/1.1"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.opengis.net/wps/1.0.0
http://schemas.opengis.net/wps/1.0.0/wpsDescribeProcess_response.xsd"
service="WPS" version="1.0.0" xml:lang="en-US">
<ProcessDescription wps:processVersion="1" storeSupported="true" statusSupported="true">
<ows:Identifier>r.grow</ows:Identifier>
<ows:Title>Generates a raster map layer with contiguous areas grown by one cell.</ows:Title>
<ows:Abstract>The manual page of this module is available here: http://grass.osgeo.org/grass70/manuals/html70_user/r.grow.html</ows:Abstract>
<ows:Metadata xlink:title="raster" />
<DataInputs>
<Input minOccurs="1" maxOccurs="1">
<ows:Identifier>input</ows:Identifier>
<ows:Title>Name of input raster map</ows:Title>
<ComplexData maximumMegabytes="2048">
<Default>
<Format>
<MimeType>image/tiff</MimeType>
</Format>
</Default>
<Supported>
<Format>
<MimeType>image/tiff</MimeType>
</Format>
<Format>
<MimeType>image/geotiff</MimeType>
</Format>
<Format>
<MimeType>application/geotiff</MimeType>
</Format>
<Format>
<MimeType>application/x-geotiff</MimeType>
</Format>
<Format>
<MimeType>image/png</MimeType>
</Format>
<Format>
<MimeType>image/gif</MimeType>
</Format>
<Format>
<MimeType>image/jpeg</MimeType>
</Format>
<Format>
<MimeType>application/x-erdas-hfa</MimeType>
</Format>
<Format>
<MimeType>application/netcdf</MimeType>
</Format>
<Format>
<MimeType>application/x-netcdf</MimeType>
</Format>
</Supported>
</ComplexData>
</Input>
<Input minOccurs="0" maxOccurs="1">
<ows:Identifier>radius</ows:Identifier>
<ows:Title>Radius of buffer in raster cells</ows:Title>
<LiteralData>
<ows:DataType ows:reference="xs:float">float</ows:DataType>
<ows:AnyValue/>
<DefaultValue>1.01</DefaultValue>
</LiteralData>
</Input>
<Input minOccurs="0" maxOccurs="1">
<ows:Identifier>metric</ows:Identifier>
<ows:Title>Metric</ows:Title>
<LiteralData>
<ows:DataType ows:reference="xs:string">string</ows:DataType>
<ows:AllowedValues>
<ows:Value>euclidean</ows:Value>
<ows:Value>maximum</ows:Value>
<ows:Value>manhattan</ows:Value>
</ows:AllowedValues>
<DefaultValue>euclidean</DefaultValue>
</LiteralData>
</Input>
<Input minOccurs="0" maxOccurs="1">
<ows:Identifier>old</ows:Identifier>
<ows:Title>Value to write for input cells which are non-NULL (-1 => NULL)</ows:Title>
<LiteralData>
<ows:DataType ows:reference="xs:integer">integer</ows:DataType>
<ows:AnyValue/>
</LiteralData>
</Input>
<Input minOccurs="0" maxOccurs="1">
<ows:Identifier>new</ows:Identifier>
<ows:Title>Value to write for "grown" cells</ows:Title>
<LiteralData>
<ows:DataType ows:reference="xs:integer">integer</ows:DataType>
<ows:AnyValue/>
</LiteralData>
</Input>
<Input minOccurs="0" maxOccurs="1">
<ows:Identifier>-m</ows:Identifier>
<ows:Title>radius is in map units rather than cells</ows:Title>
<LiteralData>
<ows:DataType ows:reference="xs:boolean">boolean</ows:DataType>
<ows:AllowedValues>
<ows:Value>true</ows:Value>
<ows:Value>false</ows:Value>
</ows:AllowedValues>
<DefaultValue>false</DefaultValue>
</LiteralData>
</Input>
<Input minOccurs="0" maxOccurs="1">
<ows:Identifier>grass_resolution_ns</ows:Identifier>
<ows:Title>Resolution of the mapset in north-south direction in meters or degrees</ows:Title>
<ows:Abstract>This parameter defines the north-south resolution of the mapset in meter or degrees, which should be used to process the input and output raster data. To enable this setting, you need to specify north-south and east-west resolution.</ows:Abstract>
<LiteralData>
<ows:DataType ows:reference="xs:float">float</ows:DataType>
<UOMs>
<Default>
<ows:UOM>meters</ows:UOM>
</Default>
<Supported>
<ows:UOM>meters</ows:UOM>
<ows:UOM>degrees</ows:UOM>
</Supported>
</UOMs>
<ows:AnyValue/>
<DefaultValue>25</DefaultValue>
</LiteralData>
</Input>
<Input minOccurs="0" maxOccurs="1">
<ows:Identifier>grass_resolution_ew</ows:Identifier>
<ows:Title>Resolution of the mapset in east-west direction in meters or degrees</ows:Title>
<ows:Abstract>This parameter defines the east-west resolution of the mapset in meters or degrees, which should be used to process the input and output raster data. To enable this setting, you need to specify north-south and east-west resolution.</ows:Abstract>
<LiteralData>
<ows:DataType ows:reference="xs:float">float</ows:DataType>
<UOMs>
<Default>
<ows:UOM>meters</ows:UOM>
</Default>
<Supported>
<ows:UOM>meters</ows:UOM>
<ows:UOM>degrees</ows:UOM>
</Supported>
</UOMs>
<ows:AnyValue/>
<DefaultValue>25</DefaultValue>
</LiteralData>
</Input>
<Input minOccurs="0" maxOccurs="1">
<ows:Identifier>grass_band_number</ows:Identifier>
<ows:Title>Band to select for processing (default is all bands)</ows:Title>
<ows:Abstract>This parameter defines band number of the input raster files which should be processed. As default all bands are processed and used as single and multiple inputs for raster modules.</ows:Abstract>
<LiteralData>
<ows:DataType ows:reference="xs:integer">integer</ows:DataType>
<ows:AnyValue/>
</LiteralData>
</Input>
</DataInputs>
<ProcessOutputs>
<Output>
<ows:Identifier>output</ows:Identifier>
<ows:Title>Name for output raster map</ows:Title>
<ComplexOutput>
<Default>
<Format>
<MimeType>image/tiff</MimeType>
</Format>
</Default>
<Supported>
<Format>
<MimeType>image/tiff</MimeType>
</Format>
<Format>
<MimeType>image/geotiff</MimeType>
</Format>
<Format>
<MimeType>application/geotiff</MimeType>
</Format>
<Format>
<MimeType>application/x-geotiff</MimeType>
</Format>
<Format>
<MimeType>application/x-erdas-hfa</MimeType>
</Format>
<Format>
<MimeType>application/netcdf</MimeType>
</Format>
<Format>
<MimeType>application/x-netcdf</MimeType>
</Format>
</Supported>
</ComplexOutput>
</Output>
</ProcessOutputs>
</ProcessDescription>
</wps:ProcessDescriptions>
WPS workflow idea
External raster maps can directly be linked into GRASS with r.external which saves time and disk space. Additionally, there is no more need to store results in the internal GRASS format - with r.external.out the resulting maps are directly written to a GDAL supported format.
Preparations
GRASS can be used in an automated way by just defining a set of variables. See here for GRASS and Shell settings and GRASS and Python.
Data flow example
The script content could be looking like this:
# register GeoTIFF file in GRASS database: r.external terra_lst1km20030314.LST_Day_1km.rst.tif out=modis_celsius # define output directory for GRASS calculation results: r.external.out /srv/gisoutput/ # do something (here: extract pixels > 20°C), write output directly as GeoTIFF: r.mapcalc "warm.tif = if(modis_celsius > 20, modis_celsius, null() )" # use the result elsewhere qgis /srv/gisoutput/warm.tif
Linking to WPS server
A framework has been developed to make the integration of GRASS GIS 7 in WPS server as easy as possible. The framework is called wps-grass-bridge and is available here:
- wps-grass-bridge: http://code.google.com/p/wps-grass-bridge/
This framework support currently PyWPS, ZOO WPS and is used by 52North WPS server. Many GRASS GIS 7 modules can be attached out of the box.
There are currently several other WPS implementations which use GRASS as GIS backbone:
- PyWPS: http://pywps.wald.intevation.org/
- PyWPS and wps-grass-bridge connector: http://code.google.com/p/wps-grass-bridge/wiki/PyWPS_Integration
- Gallery (live examples)
- PyWPS and GRASS Wiki: http://pywps.wikispaces.com/GRASS
- WPS by 52N: http://52north.org/maven/project-sites/wps/52n-wps-site/
- Connecting to GRASS out of the box: http://52north.org/maven/project-sites/wps/52n-wps-webapp/
- 52N-WPS-GRASS Demo
- ZOO project - Open OSW Platform: http://www.zoo-project.org/
References
Videos: