590 likes | 687 Views
GEOG5870: Web-based GIS Lecture 1. Oliver Duke-Williams o.w.duke-williams@leeds.ac.uk. Week 1 Introduction. Introduction to module Module structure, timetable and assessment Web-based GIS What do we mean by this? What types of web-based GIS are there? Week 1 Practical
E N D
GEOG5870: Web-based GISLecture 1 Oliver Duke-Williams o.w.duke-williams@leeds.ac.uk
Week 1 Introduction • Introduction to module • Module structure, timetable and assessment • Web-based GIS • What do we mean by this? • What types of web-based GIS are there? • Week 1 Practical • Discussion of this week’s practical task
Module structure • Blended course of face-to-face and on-line materials • Weekly practical classes • Assessment for the course is based on assessed course work
Lecture timetable • Three weekly cycle: • Week a: Face-to-face lecture • Week b: On-line lecture • Week c: On-line lecture • Each week will be accompanied with a practical class
Assessed work • The mark for the course will be based on a web-based map application produced by the student, accompanied by description of how it was produced.
Module outline • Introduction • What is ‘web-based GIS’? • Types of web maps and web GIS • OGC Web Map Servers • Google Maps • Basic and advanced use • Mapserver • Server based map applications • Local and remote data sources • Databases and spatial data • Assessed work • Planning and constructing your assessed work
Web-based GIS • What is ‘web-based GIS’? • Types of web-based GIS • Differences between web-based and other GIS • Growth in power of web-based GIS • Web Map Servers and Web Feature Servers
Does not require specialized client software However, web browsers are a heterogeneous platform Use of Javascript Use of Java Use of plugins Differing degrees of support for different graphics formats etc. Growing platform variety What is “web-based GIS” A map-based system that is delivered via a web browser “web-based GIS”
SVG example www.statistics.gov.uk/populationestimates/svg_pyramid/uk/index.html
GIS and the mobile web • Mobile web platforms have additional advantages and disadvantages • Small screen size • Constrained user input • Readily available location • Location based services
Does not require specialized client software However, web browsers are a heterogeneous platform Use of Javascript Use of Java Use of plugins Differing degrees of support for different graphics formats etc. Growing platform variety What is “web-based GIS”? A map-based system that is delivered via a web browser “web-based GIS” • Some degree of interactivity above and beyond a simple static map • That interactivity may be closely or weakly coupled with the map • A ‘true’ GIS might include • Analysis functions • Control over display of layers
Map data on the web Web mapping Web GIS Web cartography
Types of web GIS • What types of web-based GIS are there? • How might we classify them? • Examples • Classification attempts
Google Maps www.casa.ucl.ac.uk/googlemaps/OAC-super-EngScotWales.html
TrafficMap www.trafficmap.co.uk
‘Jamcams’ www.bbc.co.uk/london/jamcams_interactive_map.shtml
Weather maps www.usatoday.com/weather
Physical phenomena earthquakes.tafoni.net
Classification • Peng (2001) and Campagna and Delano (2004) has studied the use of Public Participation GIS (PPGIS) over the Internet, and have separately suggested some useful classificatory terms
Peng, 2001 • Peng describes a framework for classifying web-based public participation systems (WPPS) • Development of internet GIS • Internet as a way to disseminate digital data • Linking existing GIS programs to the web to offer simple functionality • Distributed components offering rich environment • System requirements • Exploration • Evaluation • Scenario building • Forum • WPPS enhances but does not replace traditional decision making processes
Functions and features: Peng • Internet based and platform neutral • Distributed database management • Map-based coupled with HTML based interface • Analysis models should be supported • Multiple communication channels • Proper system to support voting and expressing preferences • Highly scalable • Compatible with current standards
Increasing technical sophistication Content types Campagna and Delano • Adapted Peng’s taxonomy • Produced a Content / Technology matrix to assess public administration sites in Italy
Content examples • C1: General information • Tourist maps • Other location maps • C2: Environment and planning • Local planning applications • Submitted map documents • C3: Raw data • Raw data for users to download • C4: Analysis tools
Technology examples • T1: Static maps • Embedded images in HTML or PDF documents • T2: Interactive maps • May be integrated into the site or via a link to a 3rd party such as Multimap • T3: Interactive dynamic maps • Features may include multimedia and 3D representation • T4: Interactive map based search • Query and analysis – basic web GIS functions • T5: Web-GIS advanced functions • Planning & Support Systems
CTM surfaces for Italy From: Campagna & Delano (2004)
CTM surfaces for Denmark From: Arleth (2005)
CTM surface for Ireland From: de Róiste (2006)
Web-based GIS • What is ‘web-based GIS’? • Types of web-based GIS • Differences between web-based and other GIS • Growth in power of web-based GIS • Web Map Servers and Web Feature Servers
Differences • What are the differences between ‘web-based’ and desktop GIS? • Universality of interface • Very limited interface components on the web • Limited access to locally stored data • Limitless remote data • Processing in browser is limited • Potential of significant server-side processing power
Growth in power of web-based GIS • Recent years have seen the introduction of powerful and easy to use map based tools • Introduction of GoogleMaps is the key event in this change • These have further blurred the distinction between web-mapping and web-GIS • Dangers in the ubiquity of GoogleMaps
Onwards from Google • GoogleMaps and similar services allow users to generate map outputs using: • Map base data from Google • Projections defined by Google • Potential to use additional data in conjunction • More sophisticated services can draw from a wider range of source data • Different map bases • Different projections • In order to make sense of multiple sources, standards are required
OGC Standards • Open Geospatial Consortium control various important specifications • Services • Web Map Service (WMS) • Web Feature Service (WFS) • Web Coverage Service (WCS) • Data formats and standards • Simple Features for SQL (SFS) • Geographic Markup Language (GML) • www.opengeospatial.org
OGC Services • Use web protocols to send and receive information • Return data plus metadata • WFS – returns linear data about features • WCS – returns raster data • WMS – returns formatted graphical rendering of a map • Use web protocols to communicate between server and client
Alternate data sources • Data projected for region of interest • Privately collected data • Ad hoc data
OpenStreetMap www.openstreetmap.org
OpenStreetMap www.openstreetmap.org