GIS Tutorial 1 - South Broward Reef Dogssouthbrowardreefdogs.com/resources/Lecture2_MapDesign.pdf · 2015-08-23 · Designed Maps: A Sourcebook for GIS Users. Redlands: ESRI Press

GIS Tutorial 1

Lecture 2

Map design

Outline

Choropleth maps

Colors

Vector GIS display

GIS queries

Map layers and scale thresholds

Hyperlinks and map tips

GIS TUTORIAL 1 - Basic Workbook 2

CHOROPLETH MAPS

Lecture 2

Choropleth maps

Color-coded polygon maps

Use monochromatic scales or saturated

colors

Represent numeric values (e.g. population,

number of housing units, percentage of

vacancies)


Choropleth map example

Percentage of vacant housing units by

county

5 GIS TUTORIAL 1 - Basic Workbook

Classifying data

Process of placing data into groups (classes or

bins) that have a similar characteristic or value

Break points

Breaks the total attribute

range up into these intervals

Keep the number of intervals

as small as possible (5-7)

Use a mathematical progression

or formula instead of picking

arbitrary values


Break

points

Classifications

Natural breaks (Jenks)

Picks breaks that best group similar values

together naturally and maximizes the differences

between classes

Generally, there are relatively large jumps in

value between classes and classes are uneven

Based on a subjective decision and is the best

choice for combining similar values

Class ranges specific to the individual dataset,

thus it is difficult to compare a map with another

map


Classifications

Quantiles

Places the same number of data values in each

class

Will never have empty classes or classes with

too few or too many values

Attractive in that this method produces distinct

map patterns

Analysts use because they provide information

about the shape of the distribution.

Example: 0–25%, 25%–50%, 50%–75%,75%–

100%


Classifications

Equal intervals

Divides a set of attribute values into groups that

contain an equal range of values

Best communicates with continuous set of data

Easy to accomplish and read

Not good for clustered data

Produces map with many features in one or two classes

and some classes with no features


Classifications

Use mathematical formulas when possible.

Exponential scales

Popular method of increasing intervals

Use break values that are powers such as 2n or

3n

Generally start out with zero as an additional

class if that value appears in your data

Example: 0, 1–2, 3–4, 5–8, 9–16, and so forth


Classifications

Use mathematical formulas when possible

Increasing interval widths

Long-tailed distributions

Data distributions deviate from a bell-shaped

curve and most often are skewed to the right

with the right tail elongated

Example: Keep doubling the interval of each

category, 0–5, 5–15, 15–35, 35–75 have interval

widths of 5, 10, 20, and 40.


U.S. population by state, 2000


Original map (natural breaks)

Not good because too many values fall into low classes


Equal interval scale

Shows that an increasing width (geometric) scale is needed


Quantile scale

Custom geometric scale

Experiment with exponential scales with powers

of 2 or 3.


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:

Dividing the number of vacant housing units by the

total number of housing units yields the percentage

of vacant units

Dividing the population by area of the feature yields

a population density


Normalizing data

Nonnormalized data

Number of vacant housing units by state, 2000


Normalized data

Percentage vacant housing units by state, 2000


California population by county, 2007


Nonnormalized data


California population density, 2007

Normalized data

COLORS

Lecture 2


22

Hue is the basic color

Value is the amount of white or black in the color

Saturation refers to a color scale that ranges

from a pure hue to gray or black

GIS TUTORIAL 1 - Basic Workbook

Color overview

23

Device that provides guidance in choosing colors

Use opposite colors to

differentiate graphic features

Three or four colors equally

spaced around the wheel are

good choices for differentiating

graphic features

Use adjacent colors for

harmony, such as blue, blue

green, and green or red, red

orange, and orange


Color wheel

Light colors associated with low values

Dark colors associated with high values

Human eye is drawn to dark colors


Light vs. dark colors

Contrast

The greater the difference in value between an

object and its background, the greater the

contrast


Monochromatic color scale

Series of colors of the same hue with color

value varied from low to high

Common for choropleth maps

The darker the color in a monochromatic

scale, the more important the graphic feature

Use more light shades of a hue than dark

shades in monochromatic scales

The human eye can better differentiate among

light shades than dark shades


Monochromatic map

Values too similar


Monochromatic map

A better map, more contrast


29

An exception to the typical monochromatic

scale used in most choropleth maps

Two monochromatic scales joined together

with a low color value in the center, with color

value increasing toward both ends

Uses a natural middle point of a scale, such as

0 for some quantities (profits and losses,

increases and decreases)


Dichromatic color scale


Symmetric break points centered on 0 make it easy to

interpret the map

Dichromatic map

Color tips

Colors have meaning

Political and cultural

Cool colors

Calming

Appear smaller

Recede

Warm colors

Exciting

Overpower cool colors


32

Do not use all of the colors of the color

spectrum, as seen from a prism or in a

rainbow, for color coding

If you have relatively few points in a point

layer, or if a user will normally be zoomed in

to view parts of your map, use size instead

of color value to symbolize a numeric

attribute


Color tips

33

If you have many polygons to symbolize, it is better to

use polygon centroid points with color rather than

polygon choropleth maps.


Color tips

Changing colors in ArcMap

Choose color, more colors…


Website

http://colorbrewer2.org/

Books

Brewer, Cynthia A. 2008. Designed Maps: A

Sourcebook for GIS Users. Redlands: ESRI

Press

Brewer, Cynthia A. 2005. Designing Better Maps:

A Guide for GIS Users. Redlands: ESRI Press


Learn more about GIS colors

http://www.colormatters.com/

http://colorbrewer2.org/



VECTOR GIS DISPLAY

Lecture 2


Points, lines, polygons

Point

x,y coordinates

Line

starting and ending point and may have

additional shape vertices (points)

Polygon

three or more lines joined to form a closed area


Feature attribute tables

Store characteristics for vector features

Layers can be displayed using attributes


Displaying points

Single symbols

All CAD calls


Displaying points

Same features, different points

Based on attributes


Displaying points

Industry specific (e.g. crime analysis)

Good for large scale (zoomed in) maps


Displaying points

Industry specific (e.g. schools)

Not good for multiple features at smaller scales

Simple points better for analysis


Displaying points

Quantities

Use exaggerated sizes


Displaying lines

For analytical maps, most lines are ground

features and should be light shades (e.g. gray

or light brown)


Displaying lines

Consider using dashed lines to signify less

important line features and solid lines for the

important ones


Displaying polygons

Consider using no outline or dark gray for

boundaries of most polygons

Dark gray makes the polygons prominent

enough, but not so much that they compete for

attention with more important graphic features


Displaying polygons

Consider using texture for black and white

copies


Assign bright colors (red, orange, yellow, green,

blue) to important graphic elements

Features are known as figure

All features in figure


Graphic hierarchy

Assign drab colors to the graphic elements that

provide orientation or context, especially shades

of gray

Features known as ground

49

Circles in figure, squares and lines in

ground


Graphic hierarchy

Place a strong boundary, such as a heavy black

line, around polygons that are important to

increase figure

Use a coarse, heavy cross-hatch or pattern to

make some polygons important, placing them in

figure


Graphic hierarchy

50


Graphic hierarchy example

GIS QUERIES

Lecture 2


53

Powerful relationship between data table

and vector-based graphics—unique to GIS

Records from a feature attribute table are

selected by using query criteria

Query will automatically highlight the

corresponding graphic features


GIS queries

54

Simple query criterion

<data attribute>< logical operator><value>

NatureCode ='DRUGS'

DATE >= '20040701'

% wild card

% symbol stands for zero, one, or more characters

of any kind

NAME like ' BUR%'

Selects any crime with names starting with the

letters BUR, including burglaries (BUR), business

burglaries(BURBUS), and residential burglaries

(BURRES) GIS TUTORIAL 1 - Basic Workbook

Simple attribute queries


Simple attribute queries

56

Compound query criteria

Combine two or more simple queries with the

logical connectives AND or OR

"NATURE_COD" = 'DRUGS' AND "DATE" >

20040801

Selects records that satisfy both criteria

simultaneously

Result are drug crimes that were committed after

August 1, 2004


Compound attribute queries


Compound attribute queries

LAYER GROUPS, SCALE THRESHOLDS

Lecture 2

Layer groups

Organizes layers

Groups and names logically


Minimum scale threshold

When zoomed out beyond this scale,

features will not be visible

Tracts not visible when zoomed to the USA


Minimum scale threshold

Tracts displayed when zoomed in


Maximum scale threshold

When zoomed in, features will not be visible

State population will disappear when zoomed in

to a state


HYPERLINKS AND MAP TIPS

Lecture 2

Links images, documents, Web pages, etc.

to features on a map


Hyperlinks

Map tips

Provide an additional way to find information

about map features

Pop up as you hover the mouse pointer over

a feature


Summary

Choropleth maps

Colors

Vector GIS display

GIS queries

Map layers and scale thresholds

Hyperlinks and Map tips


GIS Tutorial 1 - South Broward Reef Dogssouthbrowardreefdogs.com/resources/Lecture2_MapDesign.pdf · 2015-08-23 · Designed Maps: A Sourcebook for GIS Users. Redlands: ESRI Press

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