Transcript Vortragstitel

GIS in the Internet - architectures, standards and
OpenSource
Team SPADE – Spatial Decision Support
GIS in the Internet - architectures, standards and OpenSource
Internet GIS-Overview
GIS in the Internet – Comparison to standard GIS
Standard GIS
Internet GIS
Data acquisition
Yes
No
Preparation, processing
Yes
No
Database connectivity
Yes
Yes
Analysis and transformation
Yes
No; Limited
Information und query
Yes
Yes
cartographic presentation
Yes; Limited
No; Limited
integration into available
interfaces
Yes; Limited
Yes
Processing of RASTER and
vector data
Yes
Yes; Limited
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GIS in the Internet – standard architectures
special application software
web-client (Browser)
LAN
WAN
GIS-Software
web server
Middleware: DBMS-Interface
Internet GIS
?
?
RDBMS
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GIS in the Internet – standard architectures
Common Restrictions for Internet-GIS:
• database connectivity: Usually only information queries possible!!
Reasons:
- data security and security permissions
- complete transactions are a complex matter!
•„thin“ Client:
the client usually gets no vector data and therefore there‘s no client-side data
transformation and analysis possible!
Reasons:
common architecture allows only „thin“ clients und „thick“ GIS-Server Tools
= „webmapserver“
 OGC (Open GIS Consortium) Specifications
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GIS in the Internet – standard interfaces and data formats
• data transmissions through http and ftp protocols!
• Raster images: gif, JPG/JPEG, PNG
• Vector graphics: XML based graphic formats:
SVG „Scalable Vector Graphics“ (W3C and Adobe), VML „Vector Markup Language“
(Microsoft) (deprecated since 1998), PGML „Precision Graphics Markup Language“,
WebCGM
and the OGC-standard: GML („Geography Markup Language“)
• 3-D visualisations: VRML „Virtual Reality Markup Language“
• standard interfaces between database and InternetGIS and between webserver and
Client:
 OGC „OpenGIS Consortium“ Specifications
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GIS in the Internet - architectures, standards and OpenSource
Internet GISSome open-source and freeware products
A) UMN MapServer
•MapServer is an OpenSource development environment for building spatially enabled
Internet applications.
•The MapServer was originally developed by (UMN) ForNet project in cooperation with NASA
and the Minnesota DNR
•Current development is funded by the TerraSIP project, a NASA sponsored project between
the UMN and consortium of land management interests.
•MapServer will run where most commercial systems won't or can't, on Linux/Apache
platforms.
•MapServer is known to compile on most UNIXes and will run under Windows NT/98/95/00.
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A) UMN MapServer: architecture
Html/Script/Java
WAN
http
request
(URL)
Raster image
or
XML text
Web Server
Cgi
-bin
Html
template
Geodata
files:
.shp
MapScript
(Perl, PHP,
Java)
.Map file
RDMS:
Oracle, MySQL...Seite 9
A) UMN MapServer: „out-of-the-box“ functions as
CGI-program
• vector formats supported: ESRI shapefiles, simple embedded features, ESRI ArcSDE
• raster formats supported: TIFF/GeoTIFF, GIF, PNG, ERDAS, JPEG and EPPL7
• fully customizable, template driven output (Html Templates)
• automatic legend and scalebar building;
feature labeling including label collision mediation;
scale dependent feature drawing
• thematic map building using logical or regular expression based classes
• feature selection by item/value, point, area or another feature
• quadtree spatial indexing for shapefiles
• support for tiled raster and vector data (display only)
• on-the-fly configuration via URLs; on-the-fly projection
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Example UMN MapServer
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B) „Degree“ Framework
• Java framework for the implementation of local and webbased distributed GIS systems
• Interfaces and formats according to OGC (Open GIS Consortium)-standards:
- GML
- WMS specification 1.1.1 (official reference implementation!)
- WFS Specification 1.0.0
- database transactions possible (so far only for attribute data)!!
• dynamic integration of distributed data ressources (cascaded WMS, WFS)
• Runs on Windows and LINUX
• Developed by the geographical institute of Bonn and lat/lon
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B) „Degree“ Framework: architecture
WAN
Web Server
local WFS
WMS-servlet
XML:
capabilities
Geodaten
files:
.shp
XML:
capabilities
WAN
http
XML
GML
Server
WFS-servlet
RDMS:
Oracle Spatial,
JDBC-databases
http requests
XML:
capabilities
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B) „Degree“ WMS: client-example
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C) OpenSource MapServer: synopsis and advantages
•Source code is accessable, degree even throuh a CVS server
•Versions available for free
•MapServer in comparison to all others is very fast
•A serverscript interface avialable for PHP and Perl (MapServer)
•GNU-Licence
•At the moment OGC Webmapping standards are being integrated:
- WMS Server
- WFS Server (degree including DB- transactions!!)
->All products support also thick clients !!
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General possible architectures for OGC mapserver
Thin (web browser)
Map Client
Thick (Java Applet)
Client:
-Display
-Rendering
Server:
-Rendering
- Generation
- Selection
of visual
elements
Client:
-Display
-Rendering
-Generation
Server:
- Generation
- Selection
of visual
elements
Server:
- Selection
of visual
elements
Thick (web map server)
Map Server
Client:
- Display
Thin (Feature Server)
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Thank You!
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