cartographic modeling output from analysis. schedule apr. 16: making maps with gis apr. 18: no class...

• Cartographic modeling

• Output from Analysis

Schedule

• 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.

• 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

Cartographic models: an example

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:

– 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 real-world 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 ConventionsFonts• 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 ConventionsPoint 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 ConventionsPolygons• 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, …

• raw count (absolute) values may present a misleading picture

• Solution:

• normalize the data

• ratio values

Thematic Mapping Issues:counts vs. ratios

• 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

Proportional Symbol 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– Client: Map user– Server: Map/spatial data provider– Viewing, browsing, sharing– Query & analysis

• ExamplesDurham Interactive MapsDurham Crime MapperThe Rome MapNational Atlas (http://nationalatlas.gov/)

allows you to download data

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 mapping• D. Wood. 2002. Mapping as a kind of 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