This document summarizes the implementation of OGC and INSPIRE standards in a geoportal. It describes the system architecture including web clients, proxy servers, and OWS servers. It discusses challenges in displaying large WFS data, implementing filter encoding, and handling axis order in WFS 1.1.0. Patches have been proposed or implemented to address issues in OpenLayers, MapServer, and OwsLib.

1. Implementing of OGC and INSPIRE Standards
From Theory to Reality
Jáchym Čepický, Štěpán Kafka
&
Tomáš Mildorf, Michal Šrédl, Přemysl Wohnout
19.05.2012 HSRS & CCSS 1
GI2012

2. System overview
Technology behind the CCSS Geoportal
WMS
WMS-T
Web Client Server proxy WFS, FES OWS Servers
WCS
WMS++ ...
HSLayers Proxy4ows  MapServer
(JavaScript) (Python)  GeoServer
 InterGraph
- OpenLayers - Mapserver / MapScript  ArcGis
- Ext - Gdal / Ogr
- OwsLib
19.05.2012 HSRS & CCSS 2
GI2012

3. Mission
Challanges & Results
 Display huge WFS data in web client → Proxy4ows
 Filter Encoding (FES) → OpenLayers, OwsLib, MapServer patches
 WFS Axis order issue → MapServer, OwsLib patches
→ some issues still remain
19.05.2012 HSRS & CCSS 3
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4. Proxy4ows
 Transforms WFS and WCS to WMS
 For WMS, it transforms the coordinate systems
 [ http://proxy4ows.org ]
 Will be presented in Prague
19.05.2012 HSRS & CCSS 4
GI2012

5. Filter Encoding
OpenLayers – <Filter_Capabilities> not parsed
Part of a WFS 1.1.0 GetCapabilities response
19.05.2012 HSRS & CCSS 5
GI2012

6. Filter Encoding
OpenLayers – <Filter_Capabilities> not parsed
Desired result
Patch proposed
- Comparison filters & related stuff
- WFS 1.0.0 and 1.1.0
19.05.2012 HSRS & CCSS 6
GI2012

7. Filter Encoding
MapServer – Filter produced as invalid XML
"wfs_filter" '<ogc:PropertyIsEqualTo xmlns:ogc="http://www.opengis.net/ogc">
<ogc:PropertyName>STUPEN</ogc:PropertyName> <ogc:Literal>3</ogc:Literal>
</ogc:PropertyIsEqualTo>' Mapfile
Mapserver code
FILTER=<ogc:Filter>
<ogc:PropertyIsEqualTo+xmlns:ogc="http://www.opengis.net/ogc">
<ogc:PropertyName>STUPEN</ogc:PropertyName>
<ogc:Literal>3</ogc:Literal> Outgoing filter
</ogc:PropertyIsEqualTo>
</ogc:Filter>
19.05.2012 HSRS & CCSS 7
GI2012

8. Filter Encoding
MapServer – Filter produced as invalid XML
"wfs_filter" '<ogc:Filter xmlns:ogc="http://www.opengis.net/ogc">
<ogc:PropertyIsEqualTo>
<ogc:PropertyName>STUPEN</ogc:PropertyName> <ogc:Literal>3</ogc:Literal>
</ogc:PropertyIsEqualTo> </ogc:Filter>' Mapfile
One-char patch
FILTER=<ogc:Filter+xmlns:ogc="http://www.opengis.net/ogc">
<ogc:PropertyIsEqualTo>
<ogc:PropertyName>STUPEN</ogc:PropertyName>
<ogc:Literal>3</ogc:Literal>
</ogc:PropertyIsEqualTo> Outgoing filter
</ogc:Filter>
19.05.2012 HSRS & CCSS 8
GI2012

9. WFS Axis Order
 WFS 1.0.0
 Axis order clearly defined in standard (East, North)
 <wfs:LatLongBoundingBox> causes confusion sometimes
 WFS 1.1.0
 As widely accepted, axis order should follow the definition of the
particular CRS
 However, not a strict requirement in the standard
 Implementations of standards differ, heaps of confusion
 Axis order depends not only on the CRS, but also on the notation used
19.05.2012 HSRS & CCSS 9
GI2012

10. WFS Axis Order
WFS 1.1.0
 Axis order depends on the SRS used
 Check http://www.epsg-registry.org/ for definitions
 BBOX url parameter
 Sometimes you need to negotiate with the service providers to
follow the definition, as otherwise no data may be returned
 Data themselves
 MapServer did not understand, that the axis order depends on
the SRS used, data was rotated by 90°
 MapServer patch provided
19.05.2012 HSRS & CCSS 10
GI2012

11. WFS Axis Order
WFS 1.1.0
Axis order depends on the notation of the SRS as well:
 EPSG:EPSG_code
→ WFS 1.0.0 style – fixed East, North
 urn:EPSG:geographicCRC:epsg_code
→ Follow-up the definition
 http://www.opengis.net/gml/srs/epsg.xml#EPSG_code
→ We don't know
19.05.2012 HSRS & CCSS 11
GI2012

12. WFS Axis Order
MapServer as WFS 1.1.0 Client
 More details here:
http://les-ejk.cz/2012/03/mapserver-as-wfs-1-1-0-client-not-suitable/
19.05.2012 HSRS & CCSS 12
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13. Patches available
OpenLayers – <Filter_Capabilities> not parsed
http://trac.osgeo.org/openlayers/ticket/3652
(Patch proposed)
MapServer – Filter produced as invalid XML
http://trac.osgeo.org/mapserver/ticket/4171
(Expected in 6.2)
MapServer – WFS Axis order
http://trac.osgeo.org/mapserver/ticket/4228
(Expected in 6.2)
OwsLib patches already deployed
19.05.2012 HSRS & CCSS 13
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14. Thank you!
Hope to see you in Prague:
19.05.2012 HSRS & CCSS 14
GI2012