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Geospatial Web
Dr. Harry Chen
CMSC 491S/691S
March 24, 2008
Agenda
Digital maps revolutionIntroduction to GISKey Geospatial Web technologies
Our civilizations are built on maps
Anglo-Saxon world map (circa 1040 CE)
1883 reconstruction of Eratosthenes' map(276-194 BC)
Babylonian World map
(6th Century BC)
Tabula Peutingeriana (4th century)- Britain to the west, India to the East
Source: http://en.wikipedia.org/wiki/Ancient_world_maps
Map is more than a piece of paper
Map by itself is a technology Gives a virtual representation of an area Tells a story about of our past history Highlights the symbolic relationships between
entities, objects and regions
Cartography – the study of map-making
World Map 1970
Source: National Geographic
Ukraine is part of the USSR
World Map 1994
Source: National Geographic
Ukrain is no longer part of the USSR
Digital Maps
Picture a digital map in your head.
What do you see?
Do you see this?
Fine. Google Maps is the most popular digital map today. But, there are many other kinds of digital maps before it. Without their innovations, we won’t have Google Maps.
Introduction to GIS
Disclaimer
This is not a geography course lecture. This is not a cartography course lecture.This lecture is not intended to cover the
full history or evolution of digital map making.
It’s intended for software developers who want to learn geospatial web programming
Key concepts
GIS (Geographic Information Systems)Geospatial Web
GIS (Geographic Information Systems)
No standard definition of what it isIn general, it’s the use of computer
systems to manage, analyze and display geographical information
We use GIS to solve problems e.g., resource management and planning
Geospatial Web
No standard definition of what it isGIS for the Web: Use GIS technology to
enhance Web application functions The Web for GIS: Use the Web as a
platform for sharing geographic data, enabling collaboration and enriching the capabilities of GIS.
Emergence of GIS
Computing technology advancements helped to establish the GIS foundation
Kind of like Paper Maps Digital Maps Pen drawing Click icons Statistical data on paper Saved data in DB
Popular use of GIS
Resource ManagementAsset ManagementUrban PlanningMarketingLogisticsSales
Technologies under the hood
GIS Foundations Data entry Data display Data management (not covered) Information retrieval and analysis (not covered)
Data entry
There’s the problem of data collection. But, we won’t discuss here.
Let’s assume you have the data collected.How do you store this data?
How would you store the information about the country border of Ukraine?
How about the border of Indonesia?
So many islands!
Irregular shapes!
How about other kinds of data?
Streets?Parcels?Evaluation?Land usage?Custom?
restaurants that the Clintons has visited
Some common representations
Raster and Vector data
The concept of layers (ESRI)
What can say about your data?
Geospatial data has two components (1) Observation (entity) (2) Attribute (variable)
Country USA (entity) Population: 301,139,947 (variable) Capital: Washington, DC (variable)
What else can you say about data?
Your data (i.e., entities) has two kinds of location information Absolute location
The exact location in a coordinates system (lat/long) Relative location
The topological location referred to other entities
UMBC (entity) N 39° 15' 19'‘, W 76° 42' 41'‘ (absolute) Located in Baltimore County (relative)
Data display
Concerns how you want to look at the data for what purpose.
Managing Your SimCity
Key Geospatial Web technologies
Geospatial Web technologies
Languages for describing geospatial data on the Web
Services for sharing and finding geospatial data on the Web
Annotate Web resources with geospatial properties
Visualizing the geospatial Web
GML
Geography Markup Language (GML) is an XML language for expressing geographic features
Defined by the Open Geospatial Consortium (OGC)
Describing a Feature using GML
http://en.wikipedia.org/wiki/Geography_Markup_Language#Examples
KML
Keyhole Markup LanguageAn XML language for expressing
geographical annotation and visualization.Developed by Keyhole, Inc. (which was
later acquired by Google)Since GML is taken, I guess they have to
stick with KML.
KML example
KML is used by Google Maps and Google Earth Less expressive than GML in terms of kind of
geographical information it can describe. But KML is more widely used in Web mashups.
Web Map Service (WMS)
WMS is a specification for implementing a Web service that can dynamically produce maps of spatially referenced data
Defined by OGC
WMS
Geo. WebApplication
ClientBrowser
Map (JPEG, GIF etc.)
Web Feature Service (WFS)
WFS is a specification for implementing a Web service that can produce descriptions of “Features” Feature is an abstract representation of any
geospatial thing in the world.
WFS
Geo. WebApplication
ClientBrowser
Feature (GML/XML or ESRI shapefiles)
Geotag
There are many ways a user can annotate Web resources with location information. Flickr machine tags Microformats RDFa GeoRSS
Visualizing the geospatial Web
2D and 3D maps are changing the way we view information on the Web
What’s next?
We will visit the following topics Google Maps API GML and KML Geonames