Browsing and downloading Spatial Data through WFS web client case National Geoportal of Finland

Transcription

1 Browsing and downloading Spatial Data through web client case National Geoportal of Finland INSPIRE conference th June, 2011 Jani Kylmäaho National Land Survey of Finland 1 NATIONAL LAND SURVEY DOWN TO EARTH

2 Browsing and downloading Spatial Data through web client case National Geoportal of Finland INSPIRE conference th June, 2011 Jani Kylmäaho National Land Survey of Finland 2 NATIONAL LAND SURVEY DOWN TO EARTH

3 Contents Finnish National Geoportal Geoportal.fi web client why? Challenges Solution Architecture Future development Conclusions 3

4 Paikkatietoikkuna Geoportal.fi National geoportal o INSPIRE DiscoveryService + Userinterfacesfor View, Download, Transformation and Registry Services o INSPIRE support site o A jointventurewithmajorgeographicalinformationdata producers in Finland Development started 2008, ongoing Open Source implementation o Based on integration of Open Source components o Free distribution of source code 4

5 2011 5

6 2011 6

7 client 7

8 web client why? INSPIRE services coming up Need for a platform-independent, easy-to-use testing environment for services Need for visualization of services o To show the linkagebetweenmapand attributedata o Support for showing attribute data more flexibly than by using WMS GetFeatureInfo o Show featuretypeson top of othermaplayers 8

9 Challenges Overall user experience o Howto make servicesmoreuserfriendly? Compatibility o Several versions of and GML standards exist o Standardsarebeingusedin a multitudeof ways Performance o Howto visualizea servicesothatitworksfluentlyin allweb browsers? o Howto preventcloggingthe servers? OpenSource o ArethereOpenSourcetoolsfor doingthis? 9

10 Solution Minimize processing done by the web browser o (Some) Web browsersarenotcapableof handlingcomplexgml structuresin an efficientway-> usejson Use a server application for processing the data o GeoToolslibrarycanhandlethe various and GML versions-> interaction with the servers using GeoTools Performance o Separate parsing for geographic and attribute data o Use of tiling, threading, timers and caching to enable smooth user experience and prevent server clogging o Predefined service- and featuretype related parameters 10

11 Architecture GEOPORTAL Internet Apache Liferay Internet Liferay Request Response PostgreSQL 11

12 Flow of actions 1 Request Response Internet 1) Add layerto map view(with1 to N feature types) 2) GeneratepictureURL:s for Ntiles 3) Generate OpenLayers requests for tiles using layerid, Bbox& ZoomLevel 4) Timerto limitthe n:o of simultaneous requests 12

13 Flow of actions 2 Apache Liferay Liferay 5) Distribute requests using Load Balancer 6) Check access rights 7) Generate requests for each featuretype based on pre-configured info (not yet requests) Request Response PostgreSQL 13

14 Flow of actions 3 8) Geoprocessing servlet with thread pooling uses GeoTools to formulate requests -> send to servers 9) There is a cache of Schemas for GeoTools -> schemas don t need to be retrieved each time a request is made Liferay Liferay Internet 14

15 Flow of actions 4 10) servers return answers which are interpreted using GeoTools (geometry) and a self-made XML parser (attributes) Liferay Internet Liferay Request Response 15

16 Flow of actions 5 Internet Apache Liferay 11)Response is relayed back to user s web browser as PNG (image) and JSON (tabular information) Liferay Request Response PostgreSQL 16

17 Conclusions Itis possibleto makean efficient clientwhich: o Works in allbrowsers o Works witha majorityof services o Performs well o Is user-friendly o Is basedon OpenSourceproducts Butittakesa lotof workto doit 17

18 Future development Possibility to download data to own computer o Mostof the work: takingcareof differentdata licensingterms Wizard for defining the service and featuretype parameters in the Geoportal Possibility to show more user friendly values in attribute table(e.g. placename service, codelist value 550 -> to be shown as Municipality ) Support for 2.0 and (stored?) queries Support for SLD visualizations of GML data 18

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20 Thank You for Your Interest! Questions / feedback: jani.kylmaaho@nls.fi 20