Thematic Mapping Techniques  Yang Shao 

 University of North Carolina at Chapel Hill

Outline• Cartogram Concept Type Challenges

• Flow map

• 3-D phenomena

• Internet Map/GIS Applications

Most commonly used method of thematic mapping

• Choropleth mapping• Proportional symbol mapping• Dot density mapping

Thematic Mapping Techniques

Additional thematic mapping techniques

• Cartograms• Flow maps• Mapping 3-D phenomena

Cartograms

•Instead of normalizing data within polygons:•We can change the polygons themselves!

•Maps that do this are known as cartograms

•Cartograms distort the size and shape of polygons to portray sizes proportional to some quantity other than physical area

Conventional Map of 2004 Election Results by State

Michael Gastner, Cosma Shalizi, and Mark Newman- University of Michiganhttp://www-personal.umich.edu/~mejn/election/

Electoral College Cartogram of 2004 Election Results by State

Michael Gastner, Cosma Shalizi, and Mark Newman- University of Michiganhttp://www-personal.umich.edu/~mejn/election/

Conventional Map of 2004 Election Results by County

Michael Gastner, Cosma Shalizi, and Mark Newman- University of Michiganhttp://www-personal.umich.edu/~mejn/election/

Population Cartogram of 2004 Election Results by County

Michael Gastner, Cosma Shalizi, and Mark Newman- University of Michiganhttp://www-personal.umich.edu/~mejn/election/

Three types of cartograms

• Non-contiguous • Contiguous• Dorling cartograms

California

http://www.ncgia.ucsb.edu/projects/Cartogram_Central/

http://www.ncgia.ucsb.edu/projects/Cartogram_Central/

http://www.ncgia.ucsb.edu/projects/Cartogram_Central/

Challenges of cartogram mapping• Recognition the displayed data the original

geographical model Shape Orientation Contiguity

• No commercial software available

Flow Map

From B.D. Dent, Cartography (1996)

Mapping 3-D phenomena

http://www.esri.com/software/arcgis/extensions/3danalyst/

3D Applications (selected examples)

• Digital urban• Geological/geophysical exploration • 3D processes such as ocean currents or

lava flows

Two kinds of volumetric phenomena

• 2.5-D phenomena have a single z value for each x and y location.

• True 3-D phenomena have multiple z values for each X and Y location.

Challenges in 3-D mapping

• Data source Land cover Houses – location, height, shape, size Roads DEM• The limitations of software

Approach: integrated use of multiple data sources

1. 2D ground plans

2. Z value from remote sensing?• Light Detection and Ranging (LIDAR)• High spatial-resolution image

3. Use local height data to extrude the building footprints detailed on high-resolution map

(Norbert Haala, Claus Brenner and Karl-Heinrich Anders)

Building height and high spatial-resolution image

x

y

Y = tan(α) × x

α

Algorithm design:

• Identify shadow (shadow vs. water) • Measure shadow size, orientation, and

shape

• Calculate building height

Shadow vs. water

3-D urban (example)

3-D urban (example)

Software considerations • Create your own 3D symbols

– Building– Vegetation– people

• 2.5-D vs. 3D

Internet Map/GIS Applications1. Location Services2. Routing and Direction services

1 and 2 are often combined together. Examples are:

www.mapblast.com - recently become a part of Microsoft

www.mapquest.com

www.yahoo.com/map

Target of these services – general public for their daily life.

3. Public notification – government can publish their spatial data using Internet map services.

Internet Map/GIS Applications(Cont.)

Example – Nuclear Waste Shipment Routes Map on Internet

http://www.state.nv.us/nucwaste/states/us.htm

4. Database query – Many public agencies are opening their databases to the public. The city of Ontario, CA, has set up an application that allows people to query the city’s parcel tax database for a specific owner or tax ID number and get a map of the parcel along with a detailed tax history of that subject. You can find similar examples in many counties and cities’ websites.

Nuclear Waste Transportation Routes

Examples of Internet Mapping Applications

Location Services

(1) Static Internet Maps – no interaction

Examples: Campus Map, Location maps for hotels, . Only permanent map is needed.

Stored as GIF or JPEG images.UNC Campus Map (GIF format):

http://www.unc.edu/courses/2001fall/engl/011/058/Pictures/campus_map.htm

Red Roof Chapel Hill Location (GIF Format):

http://www.redroof.com/reservations/inn_details.asp?innNumber=201&HD=yes

Examples of Internet Mapping Applications (Cont.)

Web Server

HTML pages with GIF or JPEG image

WebUsers Web

Users

Structure of Static Map Service

Software Requirement:HTML Editors. Anyone who can edit a html document can create a static map service. Sometime Javescript/Vbscript may be required to handle the update (like weather maps – they are static for a certain period.)

Examples of Internet Mapping Applications (Cont.)

(2) Interactive Location ServiceAs previously mentioned, mapquest, mapblast, google earth, virtual earth, and yahoo map service, etc, all provide interactive location service on Internet. These services generally target people who want to locate a place by an address (similar to geo-coding in ArcView.) or a place name. Many Internet users are using them. Users can also customize a map and print them out. Features of these services:-Customizable-Usually maps can be displayed in multiple pre-defined scales-Format of maps: JPG, GIF, etc., all compressed raster formats.-Maps can downloaded and printed, but only in a very limited size (no more than 740*800 for mapblast)-Also provide routing/directional service

Examples of Internet Mapping Applications (Cont.)

Data Server

Web Server

WebUsers Web

Users

Sending Request

Wrapping images in HTML and sending back HTML to users

Wrapping images in HTML and sending back HTML to users

Request data from server Compiling data and converting them into compressed images

Typical Structure of Interactive Location Service

Google Earth VS Virtual Earth

• Google Earth combines satellite imagery, maps and other popular geographic data. Internet users could use it to explore interested places, plan a trip, create 3D maps, etc.

http://earth.google.com/products.htmlhttp://maps.google.com/• Provides directions, interactive maps, and

satellite/aerial imagery of the United States. Can also search by keyword such as type of business.

http://local.live.com/