Introduction to Mapping Sciences: Lecture #6 (Creating Maps in GIS) Making Maps with GIS The Parts of a Map Choosing a Map Type Designing the Map

Introduction to Mapping Sciences: Lecture #6 (Creating Maps in GIS)

Making Maps with GIS

• The Parts of a Map

• Choosing a Map Type

• Designing the Map


What is a map?

• “A graphic depiction of all or part of a geographic realm in which the real-world features have been replaced by symbols in their correct spatial location at a reduced scale.”

power line


Map functions in GIS

• Storage

• Temporary communication

• Intermediate check of data

• Final report

• To be effective, must be correctly designed and constructed.


The Parts of a Map: Map Elements

The United States of America

Alaska

Lambert Conformal Conic ProjectionSource: U.S. Dept. of State

0 41 2 3

hundreds ofkilometers

0 4 0 4

Washington,D.C.National Capital

Legend

Scale

CreditsNorth ArrowPlace nameInset

Ground

Figure

Neat line Border Title

Hawaii


Cartographic Elements

• Border• Neatline• Insets

– Scale up– Scale down

• Metadata e.g. index• Off-map references



• Page coordinates

• Ground elements

• Graticule/Grid

• North arrow



• Figure– Point/Line/Area symbols

– Text

– Place Names

– Title



• Reference Information– Scale

– Projection(s)

– Sources (2)

– Credits

– Legend

– Reliability


Map “impact”

• Distribution of Employment by State 1996

• USA: Employment Distribution 1996

•U.S. Employment: 1996 Distribution

• America at Work

• Where the Jobs are Today


Text: Selection and Placement

New York

BM 232

US Route

66

200

L a

ke

M u d

POINT LINE AREAC

A

NV


Choosing Elements

• Map research

• Map compilation

• Worksheet

• Selection

• Placement

• Layout

• Tools in GIS not ideal


Choosing a Map Type

• Cartographers have designed hundreds of map types: methods of cartographic representation.

• Not all GISs allow all types.

• Most have a set of basic types

• Depends heavily on the dimension of the data to be shown in the map figure.


Choosing the Wrong Type

• Fairly common GIS error.

• Due to lack of knowledge about cartographic options.

• Can still have perfect symbolization.

• Possibility of misinformation

• Definite reduction in communication effectiveness.


Map Types: Point Data

• Reference

• Topographic

• Dot

• Picture Symbol

• Graduated Symbol


Mapping features conceived of as points

• Conceived spatial structure– exist as points– are referenced to points – are conceived of as points for mapping

purposes

• Levels of measurements – qualitative -- nominal– quantitative -- ordinal, interval, or ratio

• Symbolized with point marks


Symbolizing qualitative point data

• Show the location of features without implying a message of magnitude

• nominal scale data• appropriate visual variables

– differentiating primary variables• shape• hue• orientation

– can you use secondary variables?• Pattern arrangement, pattern orientation


Qualitative point maps

• Examples– hue– shape– orientation– pattern arrangement– pattern orientation

highly pictoralgeometric symbols mimetic symbols

Level of generalization

Qdx u v w


Symbolizing quantitative point data

• Show the location of features while implying a “message of magnitude”

• ordinal, interval, ratio scale data

• appropriate visual variables– ordering primary variables

• size• value• chroma

– can you use secondary variables?


Quantitative point maps

• Examples– Size

– Value

– Chroma

– Pattern texture

– Combinations:size and value

(Usually used together)


Graduated Symbol Map


Graduated symbol maps -- objective

• Also called “proportional symbol” maps• Symbol size varies from place to place in

proportion to the quantity it represents• Two types

– proportional -- size represents actual data values

– Classed – size represents classes of values• range graded -- size class represents a numeric

range of data (e.g., 1-10, 11-20, 21-30, 31-40, 41-50)

• ordinally scaled -- size class represents a descriptive group (e.g., low, medium, high)


Graduated symbol maps – methods

• Graduated circles often used because of– compact geometric form– ease of scaling– visual stability (less eye wandering)


Scaling Graduated Symbol Maps• Scaling determines the size of the symbols• Adjustments to scaling are sometimes made

– area is increasingly underestimated as higher magnitudes of the stimulus are judged

• Therefore, symbol sizes are adjusted to compensate for underestimation

• Methods for scaling circles– Square root method -- based on the area of the circle– Psychological scaling -- scales to reflect

underestimation by map users Values Radii500,000 1.58250,000 1.12100,000 0.71 50,000 0.50

Values Radii500,000 1.86250,000 1.25100,000 0.74 50,000 0.50


Graduated symbol maps -- methods

1. Create area proportional circles using the circle radius equation

2. Scale circle area to square root of the data or scale proportional symbols to accommodate human perception of symbols

3. Couple size with another ordering visual variable (value)

4. Show a second distribution with another ordering visual variable (value)

5. Provide legend for symbology

500,000250,000100,00050,000

250,000 to 500,000100,000 to 250,00050, 000 to 100,0000 to 50,000

very largelargemediumsmall

500,000250,000100,00050,000


Picture Symbol Map


Map Types: Line Data

• Network

• Flow

• Isopleth

• Reference


General Purpose: Reference Maps

• Network map– shows set of connected lines w/similar

attributes e.g., subway, bus/airline routes, streams/rivers

• Flow map– similar to network map, but line width varied

to show value


Simple Flow Map


Flow Map with Graduated Symbol


Map Types: Area Data

• Choropleth

• Area qualitative

• Stepped surface

• Hypsometric

• Dasymetric

• Reference


Thematic Maps

• Choropleth map– data classified and grouped within areas such

as states or counties; shaded according to value

• Area qualitative map– simple color or pattern applied to area types

e.g. land use classes: residential, agricultural, forest, wetland, tundra, water


Choropleth Map


Area Qualitative Map: Land Use

Area Qualitative Map


Map Types: Volume Data

• [Isopleth, Stepped Surface, Hypsometric]

• Gridded fishnet

• Realistic perspective

• Hill-shaded

• Image map


Volumetric Data Maps

• Stepped statistical surface– block type diagram in perspective

• Isoline map– consists of lines joining points of equal value;

surface continuity is assumed

• Contour interval map (contour map)– isoline map indicating terrain changes; e.g.,

meters or ft between contour lines


Stepped Statistical Surface Map


Colored Isoline Map


Shaded Contour Map


Choosing Types

• Check the data– Continuous– Discrete– Accuracy & Precision– Reliability

• Dimension (Point, Line, Area, Volume)• Scale of Measurment (Nominal etc.)• GIS capability• May need to supplement GIS software


Data Scaling (Stevens)

• Nominal (Name of a place)

• Ordinal (Small, med., large town)

• Interval (Arbitrary zero e.g. Sea Level)

• Ratio (Absolute zero e.g. dollars, densities)


Example: Choropleth Mapping

• Data should be AREA (e.g. States)

• Data should not suffer from area effect.

• Population?

• Per capita Income?

• Elevation? Temperature?

• Boundaries unambiguous.

• Areas non-overlapping.


Classification

• Equal Interval

• Natural groups

• N-tiles

• Equal or unequal?

• Logarithmic? Linear? Discontinuous?

• How many classes?

• Non-overlapping, distinctive groups.



The Need for Design

To appear professional and avoid errors, GIS maps should reflect cartographic knowledge about map design.

A map has a visual grammar or structure that must be understood and used if the best map design is desired.

Cartographic convention (e.g. forests should be green).


Map Design

• A GIS map is designed in a process called the design loop.

• Good map design requires that map elements be placed in a balanced arrangement within the neat line.


The Design Loop

• Create map layout as macro

• Draw on screen (proof plot)

• Look

• Edit macro

• Repeat until happy

• Make final plot


Graphic Editors


Graphic Editor Software

• Vector– Adobe Illustrator– CorelDraw– Freehand

• Raster

– Photoshop– CorelPaint– Fractal Paint


Map Design (2)

• Visual balance is affected by:

• the "weight" of the symbols

• the visual hierarchy of the symbols and elements

• the location of the elements with respect to each other and the visual center of the map.


Visual center

5% of height

5% of height

Landscape Portrait


Visual Layout

Title Here

Title Here

Eye expects (1) balance and (2) allignment


Symbol “weight”

Line weight Pattern Shading Hue


Color and Map Design

• Color is a complex visual variable and in a GIS is specified by RGB or HSI values.

• Red, Green, Blue are additive primaries.

• Magenta, Cyan and Yellow are subtractive primaries.

• Saturation and Intensity map better onto values than hue.


Dimensions of Color

HUE

SATURATION

INTENSITY


Simultaneous Contrast


Color Primaries

Subtractive color Additive color


Text placement

Santa BarbaraSanta Barbara

Santa Barbara

Santa Barbara

L a g o o n

Path right

Path Down


Scale and Generalization

• Smaller scale means fewer features.

• Smaller scale means smoother features.

• Smaller scale means combining features.

• Smaller scale means displacing features.

• Often scales are mixed or overgeneralized.


Map Design and GIS

• When a GIS map is the result of a complex analytical or modeling process, good design is essential for understanding.

• The map is what distinguishes GIS as a different approach to the management of information, so extra care should be taken to improve the final maps that a GIS generates in a GIS task.

Documents

Introduction to Mapping Sciences: Lecture #6 (Creating Maps in GIS) Making Maps with GIS The Parts of a Map Choosing a Map Type Designing the Map