Symbology - downloads2.esri.comdownloads2.esri.com/MappingCenter2007/resources/workshops/Ma… ·...
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Symbology
Transcript of Symbology - downloads2.esri.comdownloads2.esri.com/MappingCenter2007/resources/workshops/Ma… ·...
Symbology
Cartographic symbolization
Cartographic symbolization is based on“a systematic approach for selectingthe graphic symbols to use on a map”
Symbolization is the process of creating graphic symbols to represent feature attributes values
The four components of symbolization
featuredimensionality
levelof
measurement
graphicmark
visualvariables
mappingmethod
symbolization
=+ + +
The four components of symbolization
FEATUREREPRESENTATION
ATTRIBUTEREPRESENTATION
`
featuredimensionality
levelof
measurement
graphicmark
visualvariables
mappingmethod
symbolization
=+ + +
FEATURE ATTRIBUTEFEATURE
REPRESENTATIONATTRIBUTE
REPRESENTATION
`
featuredimensionality
levelof
measurement
graphicmark
visualvariables
mappingmethod
symbolization
=+ + +
The four components of symbolization
featuredimensionality
levelof
measurement
graphicmark
visualvariables
mappingmethodsymbolization
=+ + +
FEATURE ATTRIBUTEFEATURE
REPRESENTATIONATTRIBUTE
REPRESENTATION
`
The four components of symbolization
The four components of symbolization
featuredimensionality
levelof
measurement
graphicmark
visualvariables
mappingmethod
symbolization
=+ + +
Symbolization requires…
1. FEATUREFeature dimensionality -- conceptualizing the feature that is to be portrayed in terms of the extent of the phenomena
2. ATTRIBUTELevel of measurement -- selecting (and maybe changing) the level of measurement of the original data values
Four initial levels of measurement
Nominal level -- class differencesOrdinal level -- class differences and rank within classInterval level -- class differences and numerical values with an arbitrary zero valueRatio level -- class differences and numerical values with the zero value denoting absence of a feature
Reduced to Qualitative / Quantitative
Nominal level = qualitative data / information
Ordinal, interval, ratio level = quantitative or numerical data / information
Levels of measurement for cartography
Nominal qualitativeOrdinal, interval, ratio quantitative (numerical)Extensions – not in this class
Feature dimensionality (the geographic FEATURE)
0 to 3 dimensionsPoint (0-D)Line (1-D)Area (2-D)Surface (2-½)Volume (3-D)
Feature dimensionality -> spatial data models
Discrete phenomenaContinuous phenomena
Let’s look at this fromJenks’ point of view
Graphic marks (feature representation)
PointLinePolygon(Pixels, facets, etc.)
Visual variables
A reduction
QualitativeHueOrientationShapeArrangement
QuantitativeValue (Lightness)Chroma (Saturation)Spacing (Texture)Size (includes Perspective Height)
Color variables
Hue
Value / lightness
Saturation / chroma
Hue, value, saturation
Hue is the most obvious characteristic of a color Saturation is the purity of a color
High saturation colors look rich and fullLow saturation colors look dull and grayishSometimes saturation is called chroma
Value is the lightness or darkness of a color
Hue
Chroma
Value
Hue
Value
Size
Shape
Orientation of a point
Orientation of a polygon
Size
Quantitative
Arrangement
The Symbol Selection Process
Major factors underlying the symbol selection process
Level of measurementof data describing each featureof information about the feature that we want to communicate to the map reader
Spatial dimensionpoint, line, area, surface, volume
Graphic markspoint, line, area, surface (pixels, facets, etc.)
Visual variables for the different graphic marksfor the different conceived spatial structuresand for the different levels of measurement
Mapping Methods
Choropleth mapsProportional symbol mapsIsopleth mapsDot mapsDasymetric mapsPrism mapsFlow mapsCartograms
