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TOP10NL GML prototype 2nd GML Relay, 13-12-2002 Marian de Vries.

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Presentation on theme: "TOP10NL GML prototype 2nd GML Relay, 13-12-2002 Marian de Vries."— Presentation transcript:

1 TOP10NL GML prototype 2nd GML Relay, 13-12-2002 Marian de Vries

2 1st GML Relay 12 June 2001: 2 participants IONIC Software Laser-Scan Maybe too early !

3 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

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5 Overview TOP10Vector project GML: why GML: how TOP10NL GML prototype

6 TOP10Vector project Started in 2000 Project cooperation: –Topografische Dienst (= Dutch NMA) –Center for Geo Information Wageningen –ITC Enschede –Geodesy dept. TU Delft –User groups

7 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)

8 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

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10 TOP10Vector project Additional goal: –conformance to standards: OpenGIS, ISO, CEN Why? –mif, e00, dxf, SQLLoad files = vendor specific –NEN 1878 = Dutch, not international

11 Overview TOP10Vector project GML: why GML: how TOP10NL GML prototype

12 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

13 GML = XML 3586549.54,6790984.34 3586598.23,6790924.09 3586649.23,6790952.23 3586549.54,6790984.34 …

14 Dutch NEN 1878: ‘fixed position’

15 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

16 GML 2.1 geometry model Point LineString LinearRing Polygon MultiPoint MultiLineString MultiPolygon Box

17 Basic GML element ‘tree’ FeatureCollection featureMember Feature nonSpatialProperty … geometryProperty Geometry (Polygon, LineString, Point etc.) geometryProperty Geometry (Polygon, LineString, Point etc.) … nonSpatialProperty …

18 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

19 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’

20 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’...

21 GML spec. = class repository gml:AbstractFeatureCollectionType gml:FeatureAssociationType gml:AbstractFeatureType gml:GeometryPropertyType gml:AbstractGeometry gml:polygonProperty gml:lineStringProperty... gml:Polygon gml:Point... gml:coordinates gml:Box (abstract) types element names

22 From conceptual data model …

23 … to technical GML model

24 … to GML.xsd schema

25 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

26 Overview TOP10Vector project GML: why GML: how TOP10NL GML prototype

27 10 Feature types –WegDeel, WaterDeel, SpoorbaanDeel, Terrein = complete cover of surface –Gebouw –InrichtingsElement –4 ‘Gebieden’ (= Admin. Areas) feature types 7 Feature collections

28 TOP10NL GML prototype Some characteristics: –feature types with more than 1 geometry –mixed geometries –use of Xlink/XPointer –cardinality (multiplicity) of properties –...

29 Infrastructure types have 2 geometries Road, Railway, Water inherit from this type

30 Intersection: polygon + point, same id

31 Metadata per object -> XLink/XPointer 6100001 9000017 Geïnterpreteerde luchtfoto Orthogonale luchtfoto, vlieghoogte ca 3800 meter; schaal 1:18000 1998 5 meter

32 More than 1 value -> more than 1 element 2105003 6100004 2100012 5100212 … history in data: ‘originated_from’ property

33 Example 2: WegNummer (RoadNo.)

34 Null value --> no element 2110084 2001-12- 11T11:38:15+02:00... Leave ‘empty’ element out

35 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

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

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