Spatial Symbology

Thematic Data

&

Thematic Data

Language and style interrelates thematic data and spatial symbology

Understanding this language allows us to: Use appropriate cartographic symbolization and

standards Communicate messages better Critique maps using an analytical framework Make better maps

Analytic Framework

Spatial Dimension Spatial Characteristic Level of Measurement Visual Variables

Spatial Dimension

Point Line Area Volume Space-Time

Point

X Y

Geographic Coordinates

Spatial Dimension

.

0 dimensional

A Point has no extent

or area

Spatial Dimension

Dot DistributionMap

Proportional Symbol

Map

Spatial Dimension

LineSeries of

Y

X 1 Dimension

Length

Qualitative Thematic Line Map

Quantitative Thematic Line Map

Is a line always a line?

Enclosed Series of X, Y

Spatial DimensionFound on base mapsnot thematic overlays

Area

2 Dimensional

Length & Width

Spatial Dimension

Feature Model of Space

Maps as graphic representations

Spatial DimensionVolume

3 Dimensions

Surface

X Y Z

Area

+ Thematic Overlay

Nominal Area Map

Qualitative

“Z” on thematic overlay

Choropleth Map

“Z” on thematic overlay Quantitative Volumetric Map

X, Y, Z

Space-Time

4 Dimensions

Spatial Dimension

Time

+

=

Spatial Characteristic

Discrete Continuous Sequential

Discrete Phenomenon

Distinct locations in space

Does the phenomenon occur throughout an area?

Spatial Dimension

Point Phenomena=

no

Continuous Phenomenon

Does the phenomenon occur throughout an area?

YES

=Area or Volumetric Phenomena

Spatial Dimension

Sequential Phenomena Series of points in a sequence Spatial Dimension = Line

Level of Measurement

Nominal

Ordinal

Interval

Ratio

non-numeric

non-numeric

numeric

numeric

Qualitative

Quantitative

Quantitative

Quantitative

NominalLeast Accurate

No Ordering

Distinctionin Category

Ordinal Categorization & Ranking

No Numerical Differences in Kind

Interval

No Zero Point, Can’t Make Ratio Claim

Numerical Difference Between Categories

Ratio

Same as Interval

But

Non-Arbitrary Zero Point

Visual Variables

Point

Line

Area

Form Size Color Value Texture Orientation

Qualitative or Quantitative ?

Spatial Dimension?

Visual Variable?

Level of Measurement?

Volume

Spatial Characteristic? Continuous

Interval

Color

Appropriate use of Visual Variable?

Color = qualitative

Spatial Dimension?

Visual Variable?

Level of Measurement?

Point

Spatial Characteristic? Discrete

Ratio

Size Appropriate use of Visual Variable?

Size = quantitative

Spatial Dimension?

Visual Variable?

Level of Measurement?

Volume

Spatial Characteristic? Continuous

Ordinal

Color

Appropriate use of Visual Variable?

Color = qualitative

Spatial Dimension?

Visual Variable?

Level of Measurement?

Volume

Spatial Characteristic? Continuous

Nominal

Color

Appropriate use of Visual Variable? Color = qualitative

Spatial Dimension?

Visual Variable?

Level of Measurement?

Point

Spatial Characteristic? Discrete

Ratio

Color

Appropriate use of Visual Variable?

Color = qualitative

Size

Size = Quantitative

Sequential

Line