The status of the GeoServer WPS

The status of GeoServer WPS

Ing. Andrea Aime, GeoSolutions
Ing. Simone Giannecchini, GeoSolutions

FOSS4G 2011, Denver
12th-16th September 2011

Overview

 Who we are
 WPS introduction
 Vector processes
 Raster processes
 Conversion processes
 Accessing local data sources
 Chaining
 Examples
 Rendering transformations
 Limitations and wish list
 Question time
FOSS4G 2011, Denver

GeoSolutions
 Founded in Italy in 2006
 Expertise
• Image Processing, GeoSpatial Data Fusion
• Java, Java Enterprise, C++, Python
• JPEG2000, JPIP, Advanced 2D visualization
 Supporting/Developing FOSS4G projects
 GeoTools, GeoServer
 GeoBatch, GeoNetwork

 Clients
 Public Agencies
 Private Companies

 http://www.geo-solutions.it
FOSS4G 2011, Denver

WPS Quick introduction

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WPS

 Wikipedia introduces OGC WPS as:
 [A service] designed to standardize the
way that GIS calculations are made
available to the Internet.
 WPS can describe any calculation
including all of its inputs and outputs,
and trigger its execution
 The specific processes served up by a WPS
implementation are defined by the owner of that
implementation.
 Although WPS was designed to work with spatially
referenced data, it can be used with any kind of
data.
FOSS4G 2011, Denver

Capabilities document

 Some metadata
about the server
and its owner
 The list of available
processes, with a
description
 Let’s say we’re
interested in the
JTS:buffer process

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Process description

 List of inputs
and outputs
 Descriptions
 List of accepted
formats (not
shown in the
xml)

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Process execution

 Buffer a L shaped
geometry with
distance “2”
 Get the result back
as GML

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GeoServer Specifics

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GeoServer WPS history

 Started by Refractions in 2008, with limited capabilities
(only single geometry and single feature support)
 First overhaul attempt end of 2008 by the community,
added testing, support for vector collections
 New development since mid 2010, mostly new
processes and input/output formats

Refractions GS community Current activity

2008 2009 2010 2011

FOSS4G 2011, Denver

WPS: demo builder

 List processes
 Describe
 Set parameters and
execute
 All in one form

FOSS4G 2011, Denver

Inputs and outputs

FOSS4G 2011, Denver

IO setup

 Processes parameters
defined in terms of Java
objects
 Pluggable converters trade
between the java object
and the serialized
representation
 If a input is internal straight
read from the source
 Leveraging on all the
available optimizations!

FOSS4G 2011, Denver

“Primitives” IO Parameters

 Numbers: byte, short, int, long, float, double, any Number
subclass, properly mapped in XML types
 Strings and CharSequence in general
 Date, Time, Timestamp
 CoordinateReferenceSystem (EPSG:xxx and urn:… forms)

 URLs
 Range (min -> max)
 Interpolation method

FOSS4G 2011, Denver

Complexes IO Parameters

 Geometries  Vectors
 GML 2  WFS 1.0 collection
 GML 3  WFS 1.1 collection
 WKT  GeoJSON
 Rasters  Zipped shapefile
 ArcGrid  Others
 GeoTiff  SLD 1.0
 Unreferenced  OGC Filter (1.0, 1.1)
PNG/JPEG
 CQL Filter

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Open API

 Easy to plug your own custom process parameter I/O

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Available Vector processes

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JTS processes

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Example JTS process
Intersection

POLYGON ((5 10, 10 10, 10 5, 5 5, 5 10))

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Query oriented processes

 AKA “All you wanted WFS to do for you but he never
wanted to”
 gs:Aggregate: count/avg/max/median/min/stddev/sum on
a feature collection
 gs:Count: like WFS Hits, but on whatever source
 gs:Bounds: bounds of whatever source, missing from
WFS
 gs:Query: query any source like WFS
 gs:Unique: unique values of an attribute
 gs:Nearest: find the nearest features

FOSS4G 2011, Denver

Aggregation example

 Get the min, max and
sum of the PERSONS
attribute in the
topp:states layer

FOSS4G 2011, Denver

Other Vector processes

 gs:BufferFeatureCollection: buffer all features
 gs:Clip: cookie cut featuresgs:Reproject: reproject any
vector source
 gs:Simplify: DouglasPeucker simplifier, retain attributes
 gs:Snap: snap to grid
 gs:InclusionFeatureCollection: overlay and get all
features contained
 gs:IntersectionFeatureCollection: overlay and intersect,
retain attributes from both
 gs:UnionFeatureCollection: merge two collections in one
 gs:Import: save the features as a new GeoServer layer
FOSS4G 2011, Denver

Buffer example

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Geometry <=> Feature

 gs:collectGeometries: lump up all feature geometries into
a geometry collection
 gs:feature: turn a single geometry into a feature collection

MULTIPOINT (
(-74.01046109936333 40.707587626256554),
(-74.0108375113659 40.70754683896324),
(-74.01053023879955 40.70938711687079),
(-74.00857344353275 40.711945649065406),
(-74.0118315772888 40.708529961953786),
(-74.00153046439813 40.719885123828675))

FOSS4G 2011, Denver

Raster processes

FOSS4G 2011, Denver

Raster processes

 AKA “All you wanted WCS to do for you but it never
wanted to”
 Add/Multiply: add and multiply two rasters (waiting for full
algebra to be implemented)
 Crop: crop a coverage based on the specified cutting
geometry
 RangeLookup: classify raster image based on a set of
ranges ([min,max] -> value)
 ScaleCoverage: rescale and translate a given raster
 StyleCoverage: apply a SLD style to a raster, getting back a
styled (but still georeferenced) one
 Georectify: turn a non geo-referenced coverage into one
based on ground control points
FOSS4G 2011, Denver

Conversion processes

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Conversion processes
 Bridging the raster and the vector world
 Contour: extracts isolines given a set of levels or a interval
 RasterAsPointCollection: extracts one point for each cell,
with band contents as attributes
 PolygonExtraction: extracts uniform polygons from raster,
eventually given a set of value ranges
 RasterZonalStatistics: given a raster and a polygonal
compute min/max/sum/avg/stddev of the cells falling in
each polygon, return an augmented polygonal
 VectorToRaster: rasterizes vectors keeping a chosen
attribute (a CQL expression eventually) as the band value

Chaining

FOSS4G 2011, Denver

WPS Chaining
 Feed the output of a process into another process
 Allows for tree-like composition
 Let’s see a typical “clip and ship” example, both raster and
vector:
 Extract the rivers into the “restricted areas” polygons
 Extract from Blumarble any pixel in the USA

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Raster clip and ship

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Vector clip and ship

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GeoServer Integration 1: local data access

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Direct data integration
 WPS normally reads from remote WFS/WCS, parsing
GML/GeoJSON or GeoTiff/ArcGrid
 When the source is local we can dodge it though, read
directly from the source (shapefile, DBMS, geotiff)
 Hit the fictious http://geoserver/wfs url for local WFS
 Hit the fictious http://geoserver/wcs url for local WCS

Store back results (only vector)

 gs:Import: saves the
vector results into a
store of choice, and
publish as a layer
 Use right away the
new layer from
WMS/WFS/WCS/WPS
 Still missing the
equivalent for rasters

FOSS4G 2011, Denver

GeoServer Integration 2:
rendering transformations

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Rendering transformations

 On-the-fly data transformations inside rendering
chain
 Calling WPS processes from SLD docs
 Optimized for performance

FOSS4G 2011, Denver

Rendering transformations
 Point feature extraction from two band raster data (e.g.
Wind(u,v))
 Computation of direction and module from SLD
 Full SLD
 Call gs:RasterAsPointCollection
 Magnitude and direction of the arrow are computed on
the fly by using filter functions
 <WellKnownName>shape://carrow</WellKnownName>
 Working at visual resolution
 Use overviews and
decimation
 Fast with large datasets

FOSS4G 2011, Denver

Evolution and closing remarks

FOSS4G 2011, Denver

WPS*
 Deficiencies
 No support for asynchronous requests
 Missing request limits enforcements (e.g. input/output
maximum dimensions)
 Wish list:
 Scripting (Jython, GeoScript)
 Sextante, IDL, JGrass (Grass?) integration
 Improved robustness
 Jiffle (jai-tools) based raster algebra
 New layers as dynamic WPS processes (computing
data on the fly as people do WMS/WCS/WFS requests)

FOSS4G 2011, Denver

The End

Questions?
andrea.aime@geo-solutions.it
simone.giannecchini@geo-solutions.it
FOSS4G 2011, Denver

The status of the GeoServer WPS

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