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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