IICT – geo.SYSIN Towards web services dedicated to thematic mapping Olivier Ertz, Abson Sae-Tang RMLL'07, April 12 th, 2007

Roadmap of this presentation ● Describe geo.SYSIN activities ● Geographic content : primary to secondary ● CarThema Project ● FOSS webmapping technologies ● Mediamaps Project ● GOWS Project ● An overview of SLD for thematic mapping ● Possible directions for a better and complete thematic mapping support

HES- SO HEIG- VD COME M Learning TIC IICT SYSIN Research Who we are... CAP3D... TIC... Networks Institutes Units geo.SYSIN Lab (2 professors + 2 collaborators)

Zoom into the boiling points... COME M SYSIN ManagementMedia WebPrint Polypublishing - Crossmedia Content Management Systems Learning Management Systems Geographic Content Research Domains CampToCamp, IRSTV, MicroGIS... Web Service provider CMS, wiki, forum, collab platform,... Geohosting, CartoWeb, GeoServer,... HEIG School projects IICT Research projects Partnership projects

Primary Geographic content “Boundaries are purple polygons” “Bus stops are yellow points with black outline” “Boat lines are dashed blue lines” “Train lines are in red” For exploration, inventory mapping

Primary Geographic Content with filter...

Secondary geographic content The beginning of thematic mapping : ● choropleth mapping on statistic data

Symbol charts... Proportional circles pie chart histograms... Size of circle is proportional to Males + Females

CarThema Project Desktop application for thematic mapping ● Purpose : migrate old MacOS 8.x CarThema4 application to Java platform. – Partnership : MicroGIS – Client : Swiss Statistical Office ● Thematic maps : – Choropleth – Symbols : circles, triangles, character... – Complex symbol : pie chart, bars – Multi symbols, Oriented symbols – Line map, flow map...

Tons of thematic maps... Postscript AI output for high quality printing

CarThema uses gvSIG ● Open Source Mapping Framework ● Java multiplatform, Swing based ● Extensible ● Scripting ● GDBMS with SQL ! ● Layout creation ● PDF/PS output ● Closeness of community (Spain)

Styling vs. Thematic mapping ● Mapping of primary geographic content is about how to style all features of each layers on map – styles per category can be defined = filter – also symbols for point features ● Thematic mapping is about how to symbolize statistical data that belong to features – Choropleth maps with classification – Proportional symbols – Pie charts, histograms – And many more...

FOSS webmapping technologies ● Webmapping application framework : – To create a full-featured application to display, navigate and query map in a web browser – Mapserver, Cartoweb,... ● Spatial data mapping and sharing : – To render maps and share raw geographic content based on standard specification from OGC : ● WMS : map rendering ● WFS : feature servive ● SLD : style description ● Favor interoperability of geographic systems – Geoserver, Deegree,...

Web Thematic Mapping ??? ● Few FOSS applications : – Cartoweb has a geostatistical plugin ● Some proprietary solutions : – Net'Stats, Geoclip, Actimap ● Often too specific ● Not all type of thematic maps ● Do not favor interoperability : partially or not based on standard specifications

So, what's the situation ? ● Democratization of the viewing and use of primary geographic content is on the goodway, thanks to powerful webmapping tools, large respect of OGC standards, and also the recent growing of virtual globes. ● We can note a delay concerning the web mapping and sharing of secondary geographic content, what we call web thematic mapping, especially in respect of OGC standards

● Online Thematic maps – Choropleth maps – Proportionnal circles – Pie charts ● Architecture and technologies – Browser-based (IE>5.5) – Vectorial mode (Adobe SVG Plugin) – Asynchronous client/server dialog (Ajax-like) Mediamaps Project : 1 st shot towards Web Thematic Mapping Go to

GOWS Project : Standard-based web thematic mapping ● Hot focus : interoperability of geographic web services dedicated to thematic mapping ● Putting the emphasis on a web services based architecture in respect of the spatial standards from OGC and graphics ones from W3C. ● How can we use current OGC specifications for web thematic mapping ? WM S WFS SLD

Step 1 : evaluate SLD spec ● The OGC Styled Layer Descriptor (SLD) Implementation Specification is an encoding that extends the Web Map Service specification to allow user-defined symbolization of feature data. ● It allows users (or other systems) to determine which features or layers are rendered with which colors or symbols. ● How far can we go with SLD for web thematic mapping ?

SLD : filter styling capable ● One rule/style per filter ● Use of to define filter ➔ Ready for choropleth mapping Max_Oui ONU_ #00ff00

SLD : symbol size variation ● Graphic size changes with attribute size ● “Mark” graphics like square, circle, triangle, star, cross and x ➔ Ready for proportional symbols

SLD : overlaying with priorities ● Two FeatureTypeStyle : one for polygons and one for thematic layer ● Strong use of capabilities

InlineFeature : the Graal ? ● SLD 1.1 concept ● include and style a mini-dataset in SLD request ➔ 2 eyes, 1 nose, 1 mouth, 1 face ! ➔ also for pie, bar and histogram chart ?

Step 2 : some conclusions ● What about complex charts : – Juxtaposed symbols : no placement properties – Pie and bar charts : inlineFeature is clever, but such symbols are graphics not geo-graphics ! – Oriented symbols ? Flow chart ?... – For thematic mapping use, SLD becomes verbose with redundancy ● Needs some more investigations, but already we reach the limits ! ● Remember : SLD is done for styling...

Step 3 : two main directions ● Extension of SLD to support thematic mapping : – Kind of SLD-T or TLD : T = Thematic – In the follow of CpqD's work “Creating Thematic Maps with OGC Standards Through the Web”, GML Days 2005 ● Use SLD as is and just create a surrounding framework to support thematic mapping – Use basic thematic mapping capabilities of SLD – Use a specific symbol service for advanced thematic mapping

SLD-T : an extension of SLD ● Specific terminology for thematic mapping – ThematicSymbolizer, ThematicCategory ● BaseSymbolizer to avoid redundancy...

Get feature properties values ● User will need to query statistic data – WFS interface is ready for that ● User will also need to lead some operations on statistic data (aggregated or not) – WFS + OGC Function name seems interesting ● Otherwise, there is a need of new interfaces : – getHistogram : to classify client-side – getClassification : to classify server-side – getMin, getMax, getSum, getMean...

Thematic mapping Framework ● SLD permits inclusion of external graphics : ➔ (1) Statistic data queries and calculations ➔ (1') External graphics are produced by a specific service (svg, png...) ➔ (2) Ask Map Service to create the map by applying the given SLD

Conclusion and questions... ● At the moment no decision on which direction to go. Possible mix of these directions ● Stay aware of SLD evolution, need to join OGC ● Many opportunities to realize GOWS : – Example : collaboration with IRSTV team to deploy web thematic mapping for SDI Thanks for your attention ● Contact :