top10nl gml prototype 2nd gml relay, 13-12-2002 marian de vries

TOP10NL GML prototype

2nd GML Relay, 13-12-2002

Marian de Vries

1st GML Relay 12 June 2001:2 participants

IONIC Software

Laser-Scan

Maybe too early !

Why this 2nd Relay

• 1,5 year later

• more companies have invested in GML

• .. but GML is still not mainstream

• ‘data barrier’ problem not yet solved

• (GIS) users want ‘transparent’ data exchange

Overview

• TOP10Vector project

• GML: why

• GML: how

• TOP10NL GML prototype

TOP10Vector project

• Started in 2000

• Project cooperation:– Topografische Dienst (= Dutch NMA)– Center for Geo Information Wageningen– ITC Enschede– Geodesy dept. TU Delft– User groups

TOP10Vector project

• Dutch topographic data originally:– ‘old’ goal: map making– lines, points and label-points (annotiation +

symbols), ‘implicit’ polygons– no unique id’s– no feature info, only classification code

(TDN-code)

TOP10Vector project

• User groups asked for– more object-oriented data model– also non-spatial attributes (names, road

type, …)– metadata– history / temporal queries– easy aggregation (thematic, geometry)– unique id --> linking with other data

TOP10Vector project

• Additional goal:– conformance to standards: OpenGIS, ISO,

CEN

• Why? – mif, e00, dxf, SQLLoad files = vendor

specific– NEN 1878 = Dutch, not international

Overview

• TOP10Vector project

• GML: why

• GML: how

• TOP10NL GML prototype

GML= Geography Markup Language

• Has XML as technical format– ‘content’ between begin and end tags– supported by non-GIS tools– XML = eXtensible– has XML Schema as ‘data definition’

language

GML = XML

<Polygon srsName=”http://www.opengis.net/gml/srs/epsg.xml#2393”> <outerBoundaryIs> <LinearRing> <coordinates>

3586549.54,6790984.34 3586598.23,6790924.09 3586649.23,6790952.23 3586549.54,6790984.34

</coordinates> </LinearRing> </outerBoundaryIs> <innerBoundaryIs>

… </innerBoundaryIs></Polygon>

Dutch NEN 1878: ‘fixed position’01278. N200001200001 100000101top10vector 01020110100000 0 0 1 0 10103M26113 G030000 D20000101 0004I1 X161310549Y475005000 0103M25013 G030000 D20000101 0004I1 X183335225Y475005000 0103M25263 G030000 D20000101 0004I1 X160005000Y494859812 0103M24044 G110000 D19930101 0004I1 X178992927Y484947328I2 X178816060Y4852776900103M24044 G110000 D19930101 0004I1 X178882670Y484888126I2 X178705879Y4852193180103M24044 G110000 D19930101 0004I1 X177288961Y484137212I2 X177135174Y4844792350103M24044 G110000 D19930101 0004I1 X177175005Y484085750I2 X177021186Y4844277740103M24044 G110000 D19930101 0004I1 X175141766Y483726716I2 X175123406Y4841010870103M24044 G110000 D19930101 0004I1 X175274285Y483736331I2 X175255829Y4841107050103M24044 G110000 D19930101 0004I1 X173463187Y483656494I2 X173449143Y48403110801

GML fits TOP10 renewal wishes

• Is open standard (of OpenGIS Consortium, in cooperation with ISO)

• Is based on ‘object oriented’ data model:– features with spatial + non-spatial

properties, unique id’s– data oriented, not map oriented

GML 2.1 geometry model

PointLineStringLinearRingPolygonMultiPointMultiLineStringMultiPolygon

Box

Basic GML element ‘tree’

FeatureCollection featureMember Feature nonSpatialProperty nonSpatialProperty … geometryProperty Geometry (Polygon, LineString, Point etc.) geometryProperty Geometry (Polygon, LineString, Point etc.) … nonSpatialProperty …

TOP10NL GML data example<tdn:WegDeel fid="TOP10.402814"> <tdn:top10_id>2400001</tdn:top10_id> <tdn:bronRef xlink:type="simple" xlink:href="metadata.xml#TOP10.9000017"/> <tdn:object_begindatum>2001-12-17T13:24:10+02:00</tdn:object_begindatum> ... <tdn:toegankelijkheid>Openbaar</tdn:toegankelijkheid> <tdn:status>In gebruik</tdn:status> <gml:polygonProperty> <gml:Polygon srsName="EPSG:28992"> ... </gml:Polygon> </gml:polygonProperty> <gml:geometryProperty> <gml:LineString srsName="EPSG:28992"> <gml:coordinates>

106045.396,449000 105965.228,448967.705 105619.713,448827.507 </gml:coordinates> </gml:LineString> </gml:geometryProperty> <tdn:wegtype>Autosnelweg</tdn:wegtype> <tdn:hoofdverkeersgebruik>Snelverkeer</tdn:hoofdverkeersgebruik> ... <tdn:wegnummer>A12</tdn:wegnummer> <tdn:wegnummer>E25</tdn:wegnummer> <tdn:wegnummer>E30</tdn:wegnummer></tdn:WegDeel>

GML implementations

• First implementor: – Ordnance Survey Master Map

• Runners-up:– Germany (NorthRhine Westphalia)– American Census Bureau (TIGER/Line)– Dutch Topographic Service (TDN)– Scandinavia, France, ...

• Both ‘online’ (OGC WFS) and ‘offline’

GML != ready-to-use format

• you have to design your own data model

• organisation or domain specific, e.g.– for topographic data– for cadastral data– for environmental data

• each in their own ‘namespace’ ...

GML spec. = class repository

gml:AbstractFeatureCollectionTypegml:FeatureAssociationType

gml:AbstractFeatureType

gml:GeometryPropertyTypegml:AbstractGeometry

gml:polygonPropertygml:lineStringProperty ...

gml:Polygongml:Point ...

gml:coordinatesgml:Box

(abstract) types

element names

From conceptual data model …

… to technical GML model

… to GML .xsd schema<!-- ==============================================================

Type definition of Top10ObjectType (= inherited and extended by

all TOP10 feature types)

=================================================================== -->

<complexType name="Top10ObjectType" abstract="true">

<complexContent>

<extension base="gml:AbstractFeatureType">

<sequence>

<element name="top10_id" type="integer"/>

<element ref="tdn:bronRef"/>

<group ref="tdn:Temporeel"/>

<element name="dimensie" type="tdn:dimensie"/>

<element name="tdncode" type="integer"/>

</sequence>

</extension>

</complexContent>

</complexType>

Reuse of classes in GML spec.<!-- ==============================================================

Type definition of Top10ObjectType (= inherited and extended by

all TOP10 feature types)

=================================================================== -->

<complexType name="Top10ObjectType" abstract="true">

<complexContent>

<extension base="gml:AbstractFeatureType">

<sequence>

<element name="top10_id" type="integer"/>

<element ref="tdn:bronRef"/>

<group ref="tdn:Temporeel"/>

<element name="dimensie" type="tdn:dimensie"/>

<element name="tdncode" type="integer"/>

</sequence>

</extension>

</complexContent>

</complexType>

gml:AbstractFeatureCollectionTypegml:FeatureAssociationType

gml:AbstractFeatureType

gml:GeometryPropertyTypegml:AbstractGeometry

gml:polygonPropertygml:lineStringProperty ...

gml:Polygongml:Point ...

gml:coordinatesgml:Box

Overview

• TOP10Vector project

• GML: why

• GML: how

• TOP10NL GML prototype

TOP10NL GML prototype

• 10 Feature types– WegDeel, WaterDeel, SpoorbaanDeel,

Terrein = complete cover of surface– Gebouw– InrichtingsElement– 4 ‘Gebieden’ (= Admin. Areas) feature

types

• 7 Feature collections

TOP10NL GML prototype

• Some characteristics:– feature types with more than 1 geometry– mixed geometries– use of Xlink/XPointer– cardinality (multiplicity) of properties– ...

Infrastructure types have 2 geometries

<complexType name="InfrastructuurType" abstract="true"> <complexContent> <extension base="tdn:Top10ObjectType"> <sequence> <element name="type" type= .../> <element name="toegankelijkheid" type= … /> <element name="status" type="tdn:status"/> <element ref="gml:polygonProperty"/> <element ref="gml:geometryProperty"/> </sequence> </extension> </complexContent></complexType>

Road, Railway, Water inherit from this type

Intersection: polygon + point, same id

Metadata per object -> XLink/XPointer

<tdn:WaterDeel fid="TOP10.101221"> <tdn:top10_id>6100001</tdn:top10_id> <tdn:bronRef xlink:href="metadata.xml#TOP10.9000017"/>

<tdn:Bron id="TOP10.9000017"> <tdn:bron_id>9000017</tdn:bron_id> <tdn:brontype>Geïnterpreteerde luchtfoto</tdn:brontype> <tdn:bronbeschrijving>Orthogonale luchtfoto, vlieghoogte ca 3800 meter; schaal 1:18000</tdn:bronbeschrijving> <tdn:bronactualiteit>1998</tdn:bronactualiteit> <tdn:bronnauwkeurigheid>5 meter</tdn:bronnauwkeurigheid> </tdn:Bron>

More than 1 value -> more than 1 element

<tdn:WegDeel fid="TOP10.150044"> <tdn:top10_id>2105003</tdn:top10_id> <tdn:bronRef xlink:type="simple” xlink:href .../> <tdn:ontstaan_uit>6100004</tdn:ontstaan_uit> <tdn:ontstaan_uit>2100012</tdn:ontstaan_uit> <tdn:ontstaan_uit>5100212</tdn:ontstaan_uit> …

history in data: ‘originated_from’ property

Example 2: WegNummer (RoadNo.)

Null value --> no element

<tdn:WegDeel fid="TOP10.101784"> <tdn:top10_id>2110084</tdn:top10_id> <tdn:bronRef xlink:type="simple" xlink:href= .../> <tdn:ontstaan_uit></tdn:ontstaan_uit> <tdn:object_begindatum>2001-12-11T11:38:15+02:00</tdn:object_begindatum> ...

Leave ‘empty’ element out

Processing GML

• Three strategies– write data specific software (e.g. Ordnance

Survey GML importers)– offer ‘core’ compliance / only support

standard GML geometry names and data types

– try to write generic software -> parse .xsd schema first

And now … the 2nd Relay

• Will they succeed ?

• Which strategy did they choose ?

• What dangers will they encounter ...

</complexType>

<element name="Gebouw" type="tdn:GebouwType" substitutionGroup="gml:_Feature"/> <complexType name="GebouwType"> <complexContent> <extension base="tdn:Top10ObjectType"> <sequence> <element name="type" type="tdn:typeGebouw"/> <element name="functie" type="tdn:functieGebouw"/> <element name="hoogteklasse" type="tdn:hoogteklasse"/> <element name="hoogte" type="tdn:numeriekOnb"/> <element name="status" type="tdn:status"/> <element ref="gml:geometryProperty"/> <element name="hoogteniveau" type="integer" minOccurs="0"/> <element name="naam" type="string" minOccurs="0"/> </sequence> </extension> </complexContent> </complexType>

<!-- ============================================================== Declarations for InrichtingsElementen (= one of the themes)