Transcript Thematic Mapping Techniques Yang Shao University of North Carolina at Chapel Hill

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/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
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 3D symbols
– Building
– Vegetation
– people
• 2.5-D vs. 3D
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
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
Software Requirement:
HTML pages with GIF or
JPEG image
Web
Users
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 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
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
3D 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/