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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

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top10nl gml prototype

TOP10NL GML prototype

2nd GML Relay, 13-12-2002

Marian de Vries

1st gml relay 12 june 2001 2 participants
1st GML Relay 12 June 2001:2 participants

IONIC Software

Laser-Scan

Maybe too early !

why this 2nd relay
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
Overview
  • TOP10Vector project
  • GML: why
  • GML: how
  • TOP10NL GML prototype
top10vector project
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 project1
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 project2
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 project3
TOP10Vector project
  • Additional goal:
    • conformance to standards: OpenGIS, ISO, CEN
  • Why?
    • mif, e00, dxf, SQLLoad files = vendor specific
    • NEN 1878 = Dutch, not international
overview1
Overview
  • TOP10Vector project
  • GML: why
  • GML: how
  • TOP10NL GML prototype
gml geography markup language
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
slide13
GML = XML

3586549.54,6790984.34 3586598.23,6790924.09

3586649.23,6790952.23 3586549.54,6790984.34

gml fits top10 renewal wishes
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
GML 2.1 geometry model

Point

LineString

LinearRing

Polygon

MultiPoint

MultiLineString

MultiPolygon

Box

basic gml element tree
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
TOP10NL GML data example

2400001

2001-12-17T13:24:10+02:00

...

Openbaar

In gebruik

...

106045.396,449000 105965.228,448967.705 105619.713,448827.507

Autosnelweg

Snelverkeer

...

A12

E25

E30

gml implementations
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
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 spec. = class repository

(abstract) types

gml:AbstractFeatureCollectionType

gml:FeatureAssociationType

gml:AbstractFeatureType

gml:GeometryPropertyType

gml:AbstractGeometry

element names

gml:polygonProperty

gml:lineStringProperty ...

gml:Polygon

gml:Point ...

gml:coordinates

gml:Box

reuse of classes in gml spec
Reuse of classes in GML spec.

gml:AbstractFeatureCollectionType

gml:FeatureAssociationType

gml:AbstractFeatureType

gml:GeometryPropertyType

gml:AbstractGeometry

gml:polygonProperty

gml:lineStringProperty ...

gml:Polygon

gml:Point ...

gml:coordinates

gml:Box

overview2
Overview
  • TOP10Vector project
  • GML: why
  • GML: how
  • TOP10NL GML prototype
top10nl gml prototype1
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 prototype2
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
Infrastructure types have 2 geometries

Road, Railway, Water inherit from this type

metadata per object xlink xpointer
Metadata per object -> XLink/XPointer

6100001

9000017 Geïnterpreteerde luchtfoto Orthogonale luchtfoto, vlieghoogte ca 3800 meter; schaal 1:18000 1998 5 meter

more than 1 value more than 1 element
null value no element
Null value --> no element

2110084

2001-12-11T11:38:15+02:00

...

Leave ‘empty’ element out

processing gml
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
And now … the 2nd Relay
  • Will they succeed ?
  • Which strategy did they choose ?
  • What dangers will they encounter ...
slide37

substitutionGroup="gml:_Feature"/>

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