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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B6. Istanbul 2004
This infrastructure basically supports the standardized access to
geodata via web-services, as well as the adequate portrayal of
this data.
Deuce
Charactensbes e Display
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Figure 3: Cuthbert’s Portrayal Model — reference for the
visualisation pipeline (cp. May et al., 2003; Fitzke,
J. & K. Greve, 2002)
3.2.1 Available Data, Data Formats, Metadata and Data
access
The (vector) data are stored in a database (Postgis, Oracle). The
description of the data is stored in a meta-database. As the
meta-database a software developed by the Department for
Environment in Lower Saxony (^Niedersüchsisches
Umweltministerium") is used (http://www.udk-gein.de/). This
catalog-software (Umweltdatenkatalog — UDK) stores
information such as spatial reference, scale, quality, capturing
method, if necessary temporal reference, data type, availability
as well as keywords in a database and performs spatial- and
keyword-based search.
At the moment the meta-database does not conform to a
standard for describing geographic data. However from the next
version (UDK 5.0 — to be released this summer) the catalogue
software will accord to ISO/TC 211-19115, standard for
metadata and to ISO/TC 211-19119, standard for services.
The idea is to connect this meta-information catalogue to the
database storing the geodata to allow meta-information-based
selection of the geodata.
By using the meta-database's search-feature the data associated
to a keyword or an area may be identified and queried from the
database. Querying the desired geodata from the database is
accomplished by a Web Feature Server (WFS), such as the
Open-Source product Geoserver
(http://geoserver.sourceforge.net/html/index.php, OGC, 2002b).
By adding query constraints (e.g. by specifying filters) this
process corresponds to the filter-process visualized in Fig. 3.
The. Geoserver-WFS delivers data in GML 2.1.2. The
Geography Markup Language is an XML-based language. It
was developed for transport and storage of geographic
information, including both the geometry and properties of
geographic features (OGC, 2002a).
Due to the fact that the GML-specification is concerned with
the OGC Simple Features (OGC, 1999) the features’ geometry
properties is restricted to ‘simple’, such as point, curve,
linestring/line/linear ring, surface and polygon. However unlike
the Simple Feature Specification, GML allows for 3D
coordinates, but it does not directly support 3D geometry
constructs (Dorninger, P., 2003).
3.2.2 Data presentation in 2D and 3D
GML is not concerned with visualization of the data. There is
the possibility to add a Web Map Service (WMS), such as
Geoserver WMS, which delivers the data in terms of raster
maps, so no concern about visualizing the GML delivered by
WFS becomes necessary. However, following the aim to have
direct influence on visualization, like using special style or
displaying distinct data, selected by attributes in a special way,
as well as adding further functionality, the visualization process
must developed individually.
Due to the fact that GML is an XML-description for geodata, it
may be transformed — like other kinds of XML-schema — into a
25029 COUT Fire available data
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Figure 1: Architecture for the web-based geodata-infrastructure
