Harvard Government 90dn Lecture 5

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Government 90dn Mapping the Census Lecture 5: Cartography

Sumeeta Srinivasan [email protected]

Outline ƒ Map Audiences ƒ Vector GIS representation ƒ Graphic Elements – based on vectors ƒ Colors ƒ Graphical Hierarchy ƒ Map Types ƒ Normalizing Data ƒ Map Layouts ƒ Exporting Maps

Map Audiences Map Use:

Exploration

Presentation

Audience:

Trained Analyst

General Public

Map Audiences Map Use:

Exploration

Presentation

Audience: Purpose:

Trained Analyst Visual Thinking

General Public Communication

Map Audiences Map Use:

Exploration

Presentation

Audience: Purpose:

Trained Analyst Visual Thinking

General Public Communication

Advantages: Graphical

Believable

Map Audiences Map Use:

Exploration

Presentation

Audience: Purpose:

Trained Analyst Visual Thinking

General Public Communication

Advantages: Graphical Granularity: Fine

Believable Coarse

Map Audiences Map Use:

Exploration

Presentation

Audience: Purpose:

Trained Analyst Visual Thinking

General Public Communication

Advantages: Graphical Granularity: Fine

Believable Coarse

Symbols:

Mimetic

capital railroad

Abstract

Vector GIS Point Line Polygon

Points Data Attached to Points

Points Same data displayed as different points

Lines

Polygons Point Line Polygons Green Spaces Buildings Census Blocks

Jacques Bertin “What should be printed to facilitate “communication”, that  is, to tell others what we know without a loss of  information” ‐Jacques Bertin, Paris, February 1983

Bertin’s Graphic Variables Shape

Texture

Orientation

Size

Value

Hue

More Value

Saturation

Point Symbols Shape

Texture

Orientation

Size

Value

Hue

More Value

Saturation

Use Solid Point Markers

Use Three to Seven Categories Max

Orientation Shape

Texture

Orientation

Size

Value

Hue

More Value

Saturation

Texture Shape

Texture

Orientation

Size

Value

Hue

More Value

Saturation

Texture Black and White Prints Polygons Large Areas

Texture ƒ Brings object to the front (figure) ƒ long wavelength hues ƒ coarse texture

Size Shape

Texture

Orientation

Size 0-25 4-9 >9

Value

Hue

More Value

Saturation

Size Graduated Symbols Show Size or Amount

Elevated Blood Levels ( !

1 - 25

! (

26 - 50

( !

51 - 150

Value Shape

Texture

Orientation

Size

Value

Hue

More Value

Saturation

Value ƒ Increase/Decrease Contrast ƒ The greater the difference in value between an object and its background, the greater the contrast

Value ƒ By creating a pattern of dark to light values, even when the objects are equal in shape and size, it leads the eye in the direction of dark to light

Value

Value

Hue Shape

Texture

Orientation

Size

Value

Hue

More Value

Saturation

Value Shape

Texture

Orientation

Size

Value

Hue

More Value

Saturation

Saturation Shape

Texture

Orientation

Size

Value

Hue

More Value

Saturation

Saturation ƒ You can change the saturation of a hue by adding black (shadow) or white (light). The amount of saturation gives us our shades and tints.

Percentage Female-Headed Households with Children 0% to 4% 4% to 8% 8% to 12 % Grea ter than 12%

Saturation ƒ Customize the Properties…of a layer

Color Hues and Values Each of individual color is a hue Colors have meaning (i.e. cool colors, warm colors, etc) -Cool colors calming -Warm colors exciting

-Cool colors appear smaller than warm colors and they

visually recede on the page so red can visually overpower and stand out over blue even if used in equal amounts

www.colormatters.com www.colorbrewer.org

Color Wheel red orange

violet

yellow

blue green

Color Wheel ƒHarmony ƒtwo adjacent hues

red orange

violet

yellow

blue green

Color Wheel ƒHarmony ƒtwo adjacent hues

red orange

violet

yellow

blue green

Color Wheel ƒHarmony ƒtwo adjacent hues

red orange

violet

yellow

blue green

Color Wheel ƒHarmony ƒtwo adjacent hues

red orange

violet

yellow

blue

ƒContrast ƒtwo hues with one hue skipped in between

green

Color Wheel ƒHarmony ƒtwo adjacent hues

red orange

violet

yellow

blue

ƒContrast ƒtwo hues with one hue skipped in between

green

Color Wheel ƒHarmony ƒtwo adjacent hues

red orange

violet

yellow

blue

ƒContrast ƒtwo hues with one hue skipped in between

green

Color Wheel ƒHarmony ƒtwo adjacent hues

red orange

violet

yellow

blue

ƒContrast ƒtwo hues with one hue skipped in between

green

Non-Contrasting vs. Contrasting

Color Wheel ƒHarmony ƒtwo adjacent hues

red orange

violet

yellow

blue

ƒContrast ƒtwo hues with one hue skipped in between Clash ƒOpposites

green

Double-Ended Scales ƒExtremes Emphasized ƒ critical value of zero ƒ regression residuals, ƒ blue and red contrast ƒ white center is ground

red

white

blue

<-4

-4 to -2 time change -2 to 2 2 to 4 <=4

Change Map Example

Color Spot White background allows yellow color spot to be visualized

0903 0809

0604 0605

0802 0804 0507 0810

Color Spot Ramps

Graphical Hierarchy ƒGoal ƒdirect attention toward or away from available Information

Graphical Hierarchy ƒGoal ƒdirect attention toward or away from available Information

ƒFigure-Ground ƒvisual separation of a scene into recognizable figures and inconspicuous background (ground)

Graphical Hierarchy ƒGround ƒlarger of two contrasting areas

Graphical Hierarchy ƒGround ƒgrays, light browns, heavily saturated hues

Graphical Hierarchy ƒFigure ƒlong wavelength hues ƒcoarse texture

Graphical Hierarchy ƒGround

ƒFigure ƒlong wavelength hues ƒcoarse texture ƒstrong edge

Maps (Types) 1. 2. 3. 4.

Choropleth maps Isopleth maps Proportional symbol maps Dot maps

Maps (Isopleth)

Proportional symbol maps http://www.colorado.edu/geography/course s/geog_3053_s05/Lectures/Proportional%2 0Symbol%20Maps.htm

Maps (Dot density)

Cartograms (2004 Elections by County)

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

Choropleth Maps

Classifications ƒ Process of placing data into groups that have a similar characteristic or value

Classifications ƒNatural Breaks ƒClasses are based on natural groupings inherent in the data ƒLooks for where there are big jumps in data

ƒQuantiles ƒEach class contains an equal number of features ƒGood for linearly distributed data

ƒEqual Interval ƒDivides the range of attribute values into equal-sized ƒSubranges (e.g. 0–100, 101–200, and 201–300)

ƒStandard Deviation ƒCalculates mean and then maps 1-2standard deviations above / below mean

Custom Scales Know your data!

Custom Scales ƒ Edit the classifications and layer properties

Original Map

Legend State s

Total Population POP2003 -99 - 124,013 124,014 - 447,485 447,486 - 1,12 9,78 8 1,129,789 - 2,498,338 2,498,339 - 5,393,431 5,393,432 - 9,873,548

Custom Map

Total U.S. Population, 2003 0 - 9,99 9 10,000 - 24,999 25,000 - 49,999 50,000 - 99,999 100 ,000 - 499 ,999 500 ,000 - 9,873,548

Normalizing Data Divides one numeric attribute by another in order to minimize differences in values based on the size of areas or number of features in each area Examples: ƒ Dividing the 5 to 17 year-old population by the total population yields the percentage of people aged 5-17 ƒ Dividing a value by the area of the feature yields a value per unit area, or density

Normalizing Data

Normalizing Data

Percent Population 5-17 6.9% - 1 2.4 % 12.5% - 17.9% 18.0% - 23.4% 23.5% - 28.9% 29.0% - 34.4%

Map Layouts

Printed Map Layouts ƒConcise Title ƒ Topic, place, time

ƒLegend ƒ Word “Legend” or “Key” not needed

ƒData Source ƒ Source and date data was obtained

U.S. Population by County

Total U.S. Population, 2003 0 - 9,99 9 10,000 - 24,999 25,000 - 49,999 50,000 - 99,999 100 ,000 - 499 ,999 500 ,000 - 9,873,548

Data obtained from U.S. Census

Map Elements ƒ ƒ ƒ ƒ

Scale Direction Indicator Photos / Images Neat-lines

Example of a bad map...

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