• Cartographic modeling
• Output from Analysis
Schedule
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Apr. 16: Making maps with GIS
Apr. 18: No class
Apr. 23: Course review and final project
Apr. 25: Course review and final project
• May. 4 (4:00 pm) : Final Exam
Final project is due by May 4 (4:00 pm)
• Cartographic modeling
“A cartographic model provides
information through a combination of
spatial data sets, functions, and operations”
Functions and operations: reclassification,
overlay, interpolation, terrain analyses,
buffering and other proximity functions.
Cartographic models: an example
• Suitability analyses are perhaps the most
common examples of cartographic models.
• Suitability analyses rank land according to
their utility for various uses.
Cartographic models: an example
• Suitable sites:
(a) near lakes
(b) near roads
(c) not wetland
Cartographic models: an example
• Data
Lakes, roads, and hydric status
• Spatial operations
Buffering, reclassification, and overlay
Flowcharts:
Cartographic models: weightings among criteria
Criteria for a home-site selection:
1) Slopes should not be too steep
2) Sites should be far enough from a main
road to offer some privacy, but not so far as
to be isolated.
3) ?
The conversion from a qualitative to quantitative specification?
We must choose how to weight one layer
relative to another.
Home-site selection:
- How important is isolation relative to other
factors
It is often difficult to assign the relative
weights in an objective fashion
•
One methods of assigning weights is based on
their importance ranking.
1. Rank the importance
2. Calculate the relative weights according to:
Output from Analysis
GEOG370
Instructor: Yang Shao
Maps as Communication Tools
• Possibilities are many:
– GIS software readily available
– Many GIS analysts; varied levels of experience
with cartographic production & design
• So, must have mapping standards that these
many cartographers aim for
Cartographic Output
• Objective: That viewers understand the
map’s meaning
• In making a map, then, be aware of:
– The map’s purpose/intended use
– The audience
• Cartographer’s aim: Create a product that
allows knowledge transfer to the map user
Cartographic Output
• Is there one correct map?
– Monmonier (Mapping It Out)  No
• So what do you do?
– Look carefully at your data
– Experiment with different
representations/classifications
– Weigh requirements of analysis & readers’
likely perceptions
– Consider presenting multiple views of data
Thematic Map Design
• Involves a lot of decision-making:
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Scale
Projection
Symbology
Color
Organization
• Selection
• Generalization
• Placement
• So, plan ahead! &
• Allow your plan to be guided by tradition
Map elements
• Most common:
– map/spatial data
– title
– legend
– scale
– north arrow
– inset(s)
– textual information (incl. spatial metadata)
– border, neatlines
– coordinate grid
Title
• Largest and most noticeable text on the map
• Be precise! no superfluous words
• No "Map of..." in the title -- we know it's a map
Scale
• Only graphic scales will survive enlargement or reduction during
reproduction
• Some thematic maps may not need a scale bar
Legend
• Almost always required on thematic maps
• Symbolization in the legend must exactly match symbolization used on
the map
Coordinate grid
• Map must also
state coordinate
system used
Design Guidelines
Map layout - visual balance
• Based on the graphic weight (or visual weight) of the map
elements relative to the visual center
Visual contrast
• Variation and contrast will improve legibility
• Can be expressed with size, intensity, and shape of map
elements and symbolization.
Figure/Ground Relationships
• Figure: eye settles on and sees clearly
• Ground: amorphous area around the figure that map readers will not
perceive as readily
• Figure/ground relationships used to focus reader’s attention
Legibility/Clarity
• Must consider the final production medium!
– book
– poster-sized map
– computer display
– web page
• Reduction factor:
– will the map be reduced for the final version?
Simplicity
• Economy of expression
• less is frequently more
• only include elements for which you have a defensible reason for their
presence
• Compose maps as if they were essays in freshman composition course
Data Symbolization
• The cartographer/map designer must make decisions about how to
display thematic data in a map
-- generally decisions about what symbols to use to represent realworld geographic phenomena
• Variety of issues for symbolization...
– discrete vs. continuous geographic phenomena
– point, line, and area symbols
– recognize and understand nominal, ordinal, and interval/ratio
thematic data types
Cartographic Conventions
Fonts
• Usually one is enough
– But if you use more than 1
• Serif typically used for physical features (e.g., rivers, lakes)
• Sans-serif used for cultural features (names of countries, cities,
towns, streets, buildings). Why?
• Street names  Sans-serif
• Oceans, rivers, lakes, streams, other hydrographic
features  italicized serif
– Idea of flow
• Oceans & lakes  all capitals
• Rivers  capitals with lower case
• Legibility limit: 3 - 5 font
http://www.swgc.mun.ca/~cburden/2000/Cartographic%20Conventions.pdf
Cartographic Conventions
Point Features
• Label up & to the right (unless If crowds other labels or features)
• Should be parallel to the graticule
• Avoid overlapping
Linear features
• Label on top (to the north) of the line
• Rivers or streets  curve the label if necessary but place the label
where the feature bends the least
• Roads are usually solid or dashed lines, railways are hatched, and trails
are often dotted lines.
• For rivers, thoughtful placement of the labels for the main flow and
tributary can make it clear which is the tributary
– Example: Red Deer River flows into the Saskatchewan River
Red Deer River is all together but Saskatchewan is placed on the river
before the Red Deer River meets it, and the word River comes after,
making it clear that the Red Deer River is the tributary
http://www.swgc.mun.ca/~cburden/2000/Cartographic%20Conventions.pdf
Cartographic Conventions
Polygons
• Lettering for extensive land areas (e.g., Canada) should be
extended or stretched.
• As a rule, dot patterns are preferable to line patterns
– Why? Strong directional character makes line patterns disturbing
– Cross-hatched lines are OK
• Easily distinguished from dot patterns
• Available in a range of densities
• Do not have the disturbing directional character of simple parallel
lines
• If you're going to use many attributes in the legend, group
symbology
Example: 3 sub-types of one type of soil get different shades of
grey, while 3 sub-types of another type of soil get different
intensities of crosshatching and the remaining types get dots
http://www.swgc.mun.ca/~cburden/2000/Cartographic%20Conventions.pdf
Cartographic Conventions
Color
• Colour (or hue) is typically used to differentiate categories (e.g.,
commercial versus residential land uses) while color intensity is
assigned to numerical value (e.g., darker colours indicate higher
numbers or densities)
• Elevation  dark green, light green, yellow, orange, red and brown for
increasing elevations
• Bathymetry (water depth)  progressively darker blue indicates
increasing depth
• Levels of intensity are best perceived in red and least easily in yellow.
Blue also works well.
• Colors for particular features
– Highways are red; less important roads are black; contour lines are brown;
– forests and vegetative cover are green; barren/snowcapped areas are
white; hydrological features like rivers,lakes and oceans are blue; the
ground (i.e., figure background) is usually white, gray or blue (if an ocean
is involved);
Cartographic Conventions
• North is typically at the top of the map
• Map elements (e.g., scale, north arrow)  recessive
locations on the map
– Minimize dead areas  fill them up with map elements
– Nonvital areas of the map figure itself can have map elements
placed on top of them
• Map symbology should mimic the real world
– Examples: Skull & crossbones to indicate site toxicity or danger;
small triangle for a mountain summit
• Overall, avoid homogeneity (e.g., the same lettering size
for all labels, the same color for everything)
– Logical use of contrasts is the essential tool for map compositions
that are attractive and easily understood
• Strive for a balanced composition of elements
http://www.swgc.mun.ca/~cburden/2000/Cartographic%20Conventions.pdf
Thematic Mapping
• Our objectives:
– consider three very common thematic map types
• choropleth
• proportional symbol
• dot density
– understand decisions involved in classifying
quantitative data in thematic maps
Choropleth Maps
• Greek: choros (place) + plethos (filled)
• Used to map categorical and quantitative data over defined areas
– polygonal enumeration units
e.g. Census tract, county, watershed
• Polygon data values are generally classified into ranges
– allow map reader to more readily interpret the map
• Polygons can produce misleading impressions
– area/size of polygon vs. quantity of thematic data value
http://personal.uncc.edu/lagaro/cwg/color/Choropleth-5Good.gif
http://www.ilstu.edu/~jrcarter/Geo204/Choro/
Classifying Thematic Data
• Data values are classed into ranges for many thematic
maps (especially choropleth)
– aids reader’s interpretation of map
• Trade-off:
– presenting the underlying data accurately
vs.
– generalizing data using classes
• Goal is to meaningfully classify the data
– group features with similar values
– assign them the same symbol
• But how to meaningfully classify the data?
Creating Classes
• How many classes?
– too few - obscures patterns
– too many - confuses map reader
• difficult to recognize more than seven classes
• How do we create the classes?
– assign classes manually:create meaningful classes, such as
population above/below poverty level
– equal intervals: ignoring data distribution
– “natural” breaks based on data distribution: minimize
within-class variation and maximize between-class variation
– Quantiles: top 25%, 25% above middle, 25% below middle, bottom
25%
– standard deviation: mean+1s, mean-1s, mean+2s, mean-2s, …
Thematic Mapping Issues:
counts vs. ratios
• raw count (absolute) values
may present a misleading
picture
• Solution:
• normalize the data
• ratio values
Proportional Symbol Maps
• Size of symbol is proportional to size of data value
– also called graduated symbol maps
• Especially good for representing count data without
running into area distortions
• Frequently used for mapping points
– can also be used to map areas
– avoid distortions due to area size seen in choropleth
maps
http://goliath.frostburg.edu/rpotts0/ProportionalCircleMapB.jpg
Dot Density Maps
• Provide immediate picture of density over area
• 1 dot = ??? quantity of data value
– e.g. 1 dot = 500 persons
– quantity usually still associated with polygon
enumeration unit
– but, avoids some distortions seen in choropleth maps
• Placement of dots within polygon enumeration units can be
an issue
– depends on the scale of the map vs. the scale of the
enumeration units
Dot Density Maps
Map credits/source: Division of HIV/AIDS Prevention, National Center for
HIV, STD, and TB Prevention (NCHSTP), Centers for Disease Control.
http://www.unl.edu/nac/conservation/atlas/Map_Html/Demographics/National/Minority_Operated_Farms/1997.htm
Fishnet Map
http://www.kgs.ku.edu/Geophysics/4Dseismic/Reports/Jan20_2004/fig3.html
Cartograms
• Non-traditional
– Have the appearance of maps
– Spatial arrangement modified by value of
variable being measured
• Called “value by area” maps
– Can be contiguous or non-contiguous
• Contiguous: Areas are touching
• Non-contiguous: Areas are not touching
Cartogram
From B.D. Dent, Cartography (1996)
Network Map
http://virtualskies.arc.nasa.gov/research/tutorial/tutorial2b.html
Flow Map
From B.D. Dent, Cartography (1996)
Flyovers
Mapping on the Internet
• Distributed GIS
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Client: Map user
Server: Map/spatial data provider
Viewing, browsing, sharing
Query & analysis
• Examples
Durham Interactive Maps
Durham Crime Mapper
The Rome Map
National Atlas (http://nationalatlas.gov/)
Noncartographic Output
• Interactive output
– 911  electronic response
– Routing deliveries
• Map & text-based output
– Mapquest
• Map & text-based output
– Automobile onboard navigation
Non-cartographic Output
• Tables & charts
– Importance of readability
– Include if enhance mapped info
• Digital photographs
Wrapping Up
• Why is map design in GIS important?
• What kinds of decisions needs to be made
in designing and organizing maps?
• What are some types of cartographic
output? Non-cartographic output?
– Give examples of situations in which or
datasets for which the various
cartographic/non-cartographic types of output
could be used
Responsibilities
in ofmapping
• D. Wood.
2002. Mapping as a kind
talk: Brian Harley
and the confabulation of the inner and outer voice. Visual
Communication 1(2): 139-161
– What’s the inner voice?
– What’s the outer voice?
– To which are we most
responsible?
Mapping as a kind of talk: Brian Harley
and the confabulation of the inner and outer
voice
So…ethics
• Ethics: Study of morals, and the moral choices to be made
by individuals.
– Describes the rules/standards governing the conduct of members of
a society or a profession.
• Ethics: Maps & Mapmakers
– Maps are representations of the world. Mapmakers simply present
the relationships of the world. There is no ethical onus to
representing what is . . To presenting truth.
OR
– Maps are arguments presented in a two-dimensional plane,
conclusions based on data selected to advance a proposition.
Mapmakers are as responsible as anyone in any media for the
arguments they present.
Dr. Tom Koch, UBC, http://kochworks.com
Dr. Tom Koch, UBC, http://kochworks.com