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Chapter 7

Chapter 7. Visualization of Geographic Information and Generation of Information Products. Principles of cartographic design. use of color use of text symbols and symbol sets map-to-page transformation. Use of color.

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Chapter 7

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  1. Chapter 7 Visualization of Geographic Information and Generation of Information Products

  2. Principles of cartographic design use of color use of text symbols and symbol sets map-to-page transformation

  3. Use of color The primary function of color is to make information on a map visually distinguishable

  4. Dimensions of color Hue  dominant wavelength (i.e., color) Value  how light or dark a given hue is Saturation  purity of hue (range of reflected wavelengths see Figure 7.12 on color insert

  5. Hue is generally used to indicate qualitative (nominal) differences across the map area • Value and saturation are typically used to represent quantitative (ordinal, interval, or ratio) differences across the map area

  6. Note!!! It is impossible to exactly replicate colors shown on soft-copy and hard-copy since monitor colors are created by additive mixing and printer colors are created by subtractive mixing see figure 5.30

  7. Use of text • Descriptive text is used to give a map its title, to explain the legends and label features.

  8. Text characteristics: • Family Arial vs Helvetica • Style (face) bold vs italic • Font 32 point vs 48 point • Color black vs blue

  9. ArcInfo Text stored as either: (a) symbols of a coverage (b) annotation coverage

  10. Symbols and symbol sets a symbol is a graphic pattern that is used to represent a feature on a map (see Figure 7.14) • Marker symbol  points and nodes (.mrk) • Line symbols  arcs (.lin) • Shade symbols  polygons (.shd) • Text  annotation (.txt)

  11. Symbol sets each symbol must be programmed individually, so GIS software packages usually supply the user with predefined symbol sets that can be edited and customized

  12. Map-to-page transformation • Physical page  actual surface of display medium • Graphics page  portion of physical page where map is drawn • Map limits  portion of graphics page where coverage features are drawn • Map extent  area of the earth’s surface to be displayed (in actual ground units)

  13. Map-to-page transformation • Physical page  actual surface of display medium • Graphics page  portion of physical page where map is drawn • Map limits  portion of graphics page where coverage features are drawn • Map extent  area of the earth’s surface to be displayed (in actual ground units)

  14. Map composition • Map layout design • Geographical contents • Label placement

  15. Map layout design cartography is both a science and an art, therefore subjectivity and creativity play an important role in the aesthetic quality of a map see Figure 7.16

  16. Geographic contents elements to be included are governed by: • Map theme i.e., land use • Map coverage Illinois vs. U.S. • Map scale level of generalization

  17. Label placement • Good label placement ensures readability and enables the reader to associate labels with the map elements that they describe. • Guideline for automated placement of labels (see Table 7.3)

  18. Geographic contents to be considered: • Visual balance  location/proportionality • Visual clarity  generalization • Visual hierarchy  font & symbol size • Visual contrast use of color and shading • Context  selection of data layers • Text  annotation of features

  19. Cartographic generalization Why? When? How?

  20. Why? • When geographic data are gathered at a scale that is larger than the scale at which they are presented, it is necessary to reduce the complexity of the data to make the resulting map more aesthetically pleasing. • Generalization ensures that geographic data are presented at a scale appropriate to the purpose of the map and the application requirements of the user.

  21. How? (see pg. 247) • Simplification • Smoothing • Aggregation • Amalgamation • Merging • Collapse • Refinement • Typification • Exaggeration • Displacement • Classification

  22. When? • Congestion • too many features in too little space • Coalescence • features touch due to inadequate symbolization • Conflict • feature symbol incompatible with background • Complication • data from different sources or at different scales or levels of tolerance • Inconsistency • Generalization applied in a nonuniform fashion across map • Imperceptibility • Feature falls below minimum resolution of map

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