Transcript GIS Web Services

A Roadmap of Open Source
components for GI Web
Services and Clients
A Paul R Cooper
MAGIC
Outline
Overview of GI web service architecture
Standards
Databases
Web servers
GIS Server software
Client software
Close
Overview of Architecture
Overview of Web services
User interfaces with
Client Software.
Client Software talks to
Server software.
Server software
contained by Web
server.
Server Software gets
data from Data Store.
Client
Web Server
Geoserver
Datastore
Standards
Why should we be bothered?
Everyone in my field/organization uses <insert
data format>
International standards allow cross-discipline
data sharing.
GIS crosses disciplinary boundaries.
GIS allows data from different fields/disciplines
to be brought together
Discipline specific formats do not promote data
sharing across disciplines
Standards
All web services depend on standards
Geographic data use OGC standards
 (Open Geospatial Consortium)
ISO TC211 standards also important
OGC and ISO are convergent
Both depend on W3C standards
XML, CSS, HTML, XHTML, DOM

OGC standards:
Web Feature Service
http://www.opengeospatial.org/standards/wfs
Web Map Service
http://www.opengeospatial.org/standards/wms
Styled Layer Descriptor
http://www.opengeospatial.org/standards/sld
GML (also ISO 19136)
http://www.opengeospatial.org/standards/gml
Filter Encoding
http://www.opengeospatial.org/standards/filter
ISO Standards
Plenty to choose from!
Full list at http://www.isotc211.org/
Ones that are of interest to us are:
ISO 19110 (Feature Cataloguing).
ISO 19111 (Spatial Referencing by Coordinates)
ISO 19112 (Spatial Referencing by Geographic
identifier)
ISO 19115 and ISO 19139 (Metadata)
Plus lots more.
ISO standards not free, unfortunately.
Web standards
XML
http://www.w3.org/XML/
HTML and XHTML
http://www.w3.org/MarkUp/
CSS
http://www.w3.org/Style/CSS/
Document Object Model (DOM)
http://www.w3.org/DOM/

Other standards
SQL (ISO 9075 with OGC extensions)
KML (recently adopted as OGC standard;
may converge with GML)
Datastores
Datastores
Any means of storing geographic information
Spatially enabled RDBMS
l
l
l
l
PostGIS/PostgreSQL (F/OSS)
MySQL (F/OSS)
Oracle (Proprietary; Oracle Spatial not required)
ArcSDE (Proprietary)
File based
l
l
l
Shapefiles (Proprietary but published and widely used)
Images (Many formats; mostly standard)
GML (OGC standard)
Service based – other WFS servers
Web servers
Web Servers
Apache
 Stable, and well known web server.
Supports CGI based services
Web servers supporting Java
 Tomcat
 Jboss
 Jetty
 GlassFish

GIS Web Server
F/OSS Web servers
MapServer
Geoserver
Deegree
Probably lots of others!
Client Software
Client Software
Many options of varying complexity
Simple image, using a suitable URL
Custom JavaScript
OpenLayers
Google Earth
GIS Software
Using an IMG tag
Provides a static view
No interactive facilities
E.G Ship track in static context
Uses a URL specifying:
The features to be displayed
The area to be displayed
The bounding box
The SRID

Javascript based clients
WMS Calls can be scripted in JavaScript
The ADD used this approach until recently!
Advantages
Very customizable
Can be adapted to suit your environment
Disadvantages
No support
Gets complicated quite quickly!
Only supports WMS

OpenLayers
An AJAX system
Can use wide variety of data sources
WMS
WFS
Images
Actively being developed
Stable and widely used.
Documentation not wonderful!
Google Earth
Google Earth can view WMS
Some WMS will provide KML output as
an option
Geoserver does this
KML is an output from a WMS
Not a data transfer format

GIS Packages
Most mainstream GIS has at least
limited capability to use WMS/WFS.
Summary
Summary
F/OSS software provides good support for
GI Web services
F/OSS software provides good
compliance with relevant standards
F/OSS provides stable solutions
F/OSS is easy to use!
That’s All Folks!