Cartographic symbolization

Transcription

1 Symbology

2 Cartographic symbolization Cartographic symbolization is based on a systematic approach for selecting the graphic symbols to use on a map Symbolization is the process of creating graphic symbols to represent feature attributes values

3 The four components of symbolization feature dimensionality + level of measurement + graphic + mark visual variables = symbolization mapping method

4 The four components of symbolization FEATURE REPRESENTATION ATTRIBUTE REPRESENTATION feature dimensionality + level of measurement + graphic + mark visual variables = ` symbolization mapping method

5 The four components of symbolization FEATURE ATTRIBUTE FEATURE REPRESENTATION ATTRIBUTE REPRESENTATION feature dimensionality + level of measurement + graphic + mark visual variables = ` symbolization mapping method

6 The four components of symbolization FEATURE ATTRIBUTE FEATURE REPRESENTATION ATTRIBUTE REPRESENTATION feature dimensionality + level of measurement + graphic + mark visual variables = ` symbolization mapping method

7 The four components of symbolization feature dimensionality + level of measurement + graphic + mark visual variables = symbolization mapping method

8 Symbolization requires 1. FEATURE Feature dimensionality -- conceptualizing the feature that is to be portrayed in terms of the extent of the phenomena 2. ATTRIBUTE Level of measurement -- selecting (and maybe changing) the level of measurement of the original data values

9 Four initial levels of measurement Nominal level -- class differences Ordinal level -- class differences and rank within class Interval level -- class differences and numerical values with an arbitrary zero value Ratio level -- class differences and numerical values with the zero value denoting absence of a feature

10 Reduced to Qualitative / Quantitative Nominal level = qualitative data / information Ordinal, interval, ratio level = quantitative or numerical data / information

11 Levels of measurement for cartography Nominal qualitative Ordinal, interval, ratio quantitative (numerical) Extensions not in this class

12 Feature dimensionality (the geographic FEATURE) 0 to 3 dimensions Point (0-D) Line (1-D) Area (2-D) Surface (2-½) Volume (3-D)

13 Feature dimensionality -> spatial data models Discrete phenomena Continuous phenomena Let s look at this from Jenks point of view

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21 Graphic marks (feature representation) Point Line Polygon (Pixels, facets, etc.)

22 Visual variables

23 A reduction Qualitative Hue Orientation Shape Arrangement Quantitative Value (Lightness) Chroma (Saturation) Spacing (Texture) Size (includes Perspective Height)

24 Color variables Hue Value / lightness Saturation / chroma

25 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 full Low saturation colors look dull and grayish Sometimes saturation is called chroma Value is the lightness or darkness of a color Hue Chroma Value

26 Hue

27 Value

28 Size

29 Shape

30 Orientation of a point

31 Orientation of a polygon

32 Size Quantitative

33 Arrangement

34 The Symbol Selection Process Major factors underlying the symbol selection process Level of measurement of data describing each feature of information about the feature that we want to communicate to the map reader Spatial dimension point, line, area, surface, volume Graphic marks point, line, area, surface (pixels, facets, etc.) Visual variables for the different graphic marks for the different conceived spatial structures and for the different levels of measurement

35 Mapping Methods Choropleth maps Proportional symbol maps Isopleth maps Dot maps Dasymetric maps Prism maps Flow maps Cartograms

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