Thematic Mapping Techniques Yang Shao University of North

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

Thematic Mapping Techniques Most commonly used method of thematic mapping • Choropleth mapping • Proportional symbol mapping • Dot density mapping

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 Michigan http: //www-personal. umich. edu/~mejn/election/

Electoral College Cartogram of 2004 Election Results by State Michael Gastner, Cosma Shalizi, and Mark Newman- University of Michigan http: //www-personal. umich. edu/~mejn/election/

Conventional Map of 2004 Election Results by County Michael Gastner, Cosma Shalizi, and Mark Newman- University of Michigan http: //www-personal. umich. edu/~mejn/election/

Population Cartogram of 2004 Election Results by County Michael Gastner, Cosma Shalizi, and Mark Newman- University of Michigan http: //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 geographical model the original 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/3 danalyst/

3 D Applications (selected examples) • Digital urban • Geological/geophysical exploration • 3 D 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. 2 D 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

Y = tan(α) × x y α x

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 3 D symbols – Building – Vegetation – people • 2. 5 -D vs. 3 D

Internet Map/GIS Applications 1. Location Services 2. 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 (2) 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/2001 fall/engl/011/058/Pictures/campus_map. htm Red Roof Chapel Hill Location (GIF Format): http: //www. redroof. com/reservations/inn_details. asp? inn. Number=201&HD=yes

Examples of Internet Mapping Applications (Cont. ) Web Server Software Requirement: HTML pages with GIF or JPEG image Web Users Structure of Static Map Service 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 Service As 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 Arc. View. ) 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 Request data from server Wrapping images in HTML and sending back HTML to users Web Users Compiling data and converting them into compressed images Web Server Wrapping images in HTML and sending back HTML to users Sending Request Web Users 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 3 D maps, etc. http: //earth. google. com/products. html http: //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/