GIS in the Internet - architectures, standards and OpenSource

Team SPADE – Spatial Decision SupportTeam SPADE – Spatial Decision Support

GIS in the Internet - architectures, standards and

OpenSource

Internet GIS-Overview

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GIS in the Internet – Comparison to standard GIS

Standard GIS Internet GISData 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

RDBMS

Middleware: DBMS-Interface Internet GIS

GIS-Software web server

WAN

special application software web-client (Browser)

?

LAN ?

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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

GIS in the Internet – standard architectures

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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

GIS in the Internet - architectures, standards and

OpenSource

Internet GIS- Some open-source and freeware products

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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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Web Server

A) UMN MapServer: architecture

RDMS:Oracle, MySQL...

Geodatafiles:.shp

MapScript(Perl, PHP,

Java)

Cgi-bin

.Map file

Html/Script/JavaWAN

Htmltemplate

httprequest (URL)

Raster imageor XML text

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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

Web Server

RDMS:Oracle Spatial, JDBC-databases

Geodatenfiles:.shp

XML:capabilities

WAN

Server

WFS-servlet XML:capabilities

local WFS WMS-servlet

XML:capabilities

WAN

httpXMLGML

http requests

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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

Thick (web map server) Map Server Thin (Feature Server)

Thin (web browser) Map Client Thick (Java Applet)

Client:- Display

Server:-Rendering

- Generation- Selectionof visualelements

Server:- Generation- Selectionof visualelements

Client:-Display

-Rendering

Client:-Display

-Rendering-Generation

Server:- Selectionof visualelements

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Thank You!