Geography Markup Language Digital Geographic Information Working Group Conference Vancouver, 09 April, 2003 Milan Trninić [email protected]

Geography Markup Language

Digital Geographic Information Working Group ConferenceVancouver, 09 April, 2003

Milan Trninić[email protected]

Vancouver, April 09, 2003Digital Geographic Information Working Group Conference

Galdos Systems

A young, fast moving software company focused on XML and Web-Services for Geo-spatial information systemsRon Lake, the owner and CEO was founding member of OGC (1993). Creator of Geography Markup Language.Lead participant in OGC standards efforts including GML, WFS, WCS since 1998.Expertise in Analysis/Design/Build, GML Application Schema development, XML Applications (XSD / XML / SVG / XSLT / SOAP / WSDL etc.), Java client/server side development (J2ME J2EE), OGC & ISO TC/211 TC204 Standards


GML History

Feb 99 – White paper by Galdos on XML for spatial.Feb 99 – Presentation by NTT DataSummer 99 – Xbed Group led by Galdos Systems, develops SFXML (Oracle, NTT Data, MapInfo)October 99 – Galdos Systems writes GML RFC, in December it becomes publicMay 2000 – GML 1.0 Passed as recommendation paper.Feb 2001 – OGC publishes GML 2.0March 2001 – GML 2.0 voted as “adopted specification”July 2001 – GML 3.0 Workshop in Vancouver2001 – Work on GML3.0 in progress. Work on harmonizing G-XML and GML3.0 in progress.Sept 2001 – OGC votes to send GML to ISO2002 – Work on GML3.0 in progressFebruary 2003 – OGC releases GML3.0 Specification


GML OverviewWhat is it?

OGC Endorsed “Adopted Specification”. A “lingua franca” for geographic information.XML technology for handling spatial data on the Internet.Emerging international standard for spatial data—endorsed by 200 + companies and agencies around the world.Converged with G-XML (Japan) – additional 600 companies.


GML OverviewWhat is it?

Data transport Data modeling language - build application vocabularies for specific domains. Create types for geo-spatial web service Data store model. Links between elements can exist across the Internet. Links can represent relationships (e.g. spatial)


GML Overview

GML focuses on content and separates content and presentationGML data can be read and understood by people. Easily transformed.GML can enable distributed spatial datasets that are linked together – local maintenance & development /global access. Reduced cost for dataGML data can easily be mixed with non-spatial data including text, video, and imagery.GML can build shareable application schemas for various applications like telecommunications, utilities, forestry, tourism, location-based services, etc.Enables creation and easy discovery of typed services. Provides a standard means to define input & output arguments.GML is non-proprietary and open! Enables non-proprietary web feature servers, image/map annotation, map styling, spatial analysis, etc.


GML OverviewMajor elements of GML

Feature modelGeometry (2D, “2.5D”, 3D)TopologyCoveragePresentation - stylingCoordinate Reference SystemsUnits Of MeasureMeta dataDictionariesTemporal (moving objects)Observations


GML Feature Model

Developed in GML2.0Based on OGC Abstract SpecificationFeature model of ISO 19109 matches GML (GML is a subset). Enables complex features & feature associations


GML Feature ModelProperties

<RadioTower>

<position> <Point>…</Point> </position>

<footprint> <Polygon>…</Polygon> </footprint>

<radioCoverage> <Polygon>…</Polygon> </radioCoverage>

<name>KCFL</name>

</RadioTower>

Property of a feature describes its role in the feature


GML Feature ModelProperties

<position>

<Point gml:id=“P001”>

<coordinates>…</coordinates>

</Point>

</position>

Value

<property xlink:href=“http://….#P001”/>

Property value can be inline

Property value can be remote

<property>

</property>

=

<property xlink:href=“...”/>

Value

=


GML Geometry

ISO 19107 compliant0D, 1D (linear, arcs, bezier, splines), 2D“2.5D” Geometries (2D in 3D), 3D (solids with holes)Geometry Aggregates and Geometry Complexes

<Street>

<name>Robson</name>

<centerLineOf>

<LineString gml:id=“LS001” srsName=“EPSG:4326”>

<coordinates>49.29,-123.135 49.28,-123.115</coordinates>

</LineString>

</centerLineOf>

</Street>


GML Geometry

<Street>

<name>Robson</name>

<centerLineOf>

<CompositeCurve id="CC1“ srsName=“EPSG:4326”>

<curveMember>

<LineString id="C11">

<coordinates> >49.29,-123.135 49.285,-123.125</coordinates> </LineString>

</curveMember>

<curveMember>

<LineString id="C12">

<coordinates> >49.285,-123.125 49.28,-123.115</coordinates> </LineString>

</curveMember>

</CompositeCurve> </centerLineOf>

</Street>


GML Topology

ISO 19107 compliantNodes, Edges, Faces and SolidsTopological complexesTopology can be described as a part of a feature or outside of features (e.g. topology of all city streets)


GML Topology

<Route gml:id=“Bus21Route">

<topoCurveProperty>

<TopoCurve>

<directedEdge orientation="+" xlink:href="#e5"/>

<directedEdge orientation="+" xlink:href="#e3"/>

</TopoCurve>

</topoCurveProperty>

</Route>

...

<Node id="n3"/>

<Node id="n4"/>

<Edge id="e3">

<directedNode orientation="-" xlink:href="#n3"/>

<directedNode orientation="+" xlink:href="#n4"/>

</Edge>

...


GML Geometry and Topology

GML


GML Coverage

ISO 19123 compliantA coverage is a GML featureGridded coverage, segmented curves, surface tessellation Data can be binary (file), Comma Separated Values (CSV), XMLEasy to express things like distribution of measurement (temperature, pressure) over some geographic region.


GML Temporal Model

ISO 19108 compliantCovers most of the temporal types from the ISO 19108Support for dynamic feature (jointly feature and temporal model)Supports the notion of “History”Time stamping on feature or property level


GML Meta Data


GML Default Styling

Focuses on feature stylingUses Scalable Vector Graphics (SVG) and Cascading Style Sheet 2 directlyCapability to define styles for feature properties of different kindsGeometry styling and topology stylingAbility to describe animation stylesParameterized styles – the output depends on values of feature properties


GML Default StylingSymbol Libraries

Symbol Libraries – created separately and used in GML styles

Online Symbol Library (XML)

<Feature/>

<defaultStyle>

Inline symbol definition using SVG and CSS2

</defaultStyle>

<defaultStyle xlink:href=“...”/>

</Feature>


GML Default Styling and SLD

Styled Layer Description – an OGC specificationSLD has different scope – describes layers and layer styles – pertains to WMSGML styling mechanism describes feature styles – can be used in any application that uses GMLEfforts under way to harmonize GML Styling and SLD


GML Coordinate Reference Systems

Emerged from work done in OGC CRS WG and GML3.0 WGComplete schemas for description of all aspects of CRS (SRS)Definitions also exist for accuracy, data quality, units of measure etc.CRS defined in form of libraries and used from various applications, or referred to from the GML data directly


GML Coordinate Reference Systems

<LineString gml:id=“LS001” srsName=“EPSG:4326”>

<coordinates>49.29,-123.135 49.28,-123.115</coordinates>

</LineString>

<gml:GeographicCRS gml:id="urn:epsg:v6.1:crs:4326">

<ogc:dataSource>EPSG</ogc:dataSource>

<ogc:revisionDate>6/2/1995</ogc:revisionDate>

<gml:name>WGS 84</gml:name>

<gml:scope>Used by the GPS satellite navigation system and for NATO military geodetic surveying.</gml:scope>

<gml:usesCoordinateSystem xlink:href="urn:epsg:v6.1:cs:6402"/>

<gml:usesDatum xlink:href="urn:epsg:v6.1:datum:6326"/>

</gml:GeographicCRS>

Online CRS Registry


GML and ISO

GML 3.0 is the baseline for ISO GML. We do not expect major changes in GML in order for GML to become an ISO specification (ISO 19136)There are no serious compliance issues - a joint meeting (ISO and OGC) was held in Annapolis and this was discussed at length OGC and ISO have agreed to create an integrated task force and produce a single specification Joint task force to meet in May and likely also in Vancouver in July. We anticipate GML will be an ISO DIS by Dec 2003 or Jan 2004.


GML Performance


GML Applications


GML Future


GML Notes

GML Dev Days in Vancouver, July 2003First book on GML: “GML Guide” presently in print

Documents

Geography Markup Language Digital Geographic Information Working Group Conference Vancouver, 09 April, 2003 Milan Trninić [email protected]