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Symbolization

FOR357/557. Symbolization. The key to effective mapping. Overview. Introduction to module 2 Concept of layers Brewer’s on-line help Examples. Module 2 Lesson 1. Working with Symbols Types of symbols Choosing symbols Labeling map features Display and label map features. Exercise.

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Symbolization

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  1. FOR357/557 Symbolization The key to effective mapping

  2. Overview • Introduction to module 2 • Concept of layers • Brewer’s on-line help • Examples

  3. Module 2 Lesson 1 • Working with Symbols • Types of symbols • Choosing symbols • Labeling map features • Display and label map features Exercise

  4. Lines Polys Points Types of Symbols

  5. Labeling feaures • Features can be labeled with data in the attribute file • Set up in Layer Properties • Turn on and off with right-click on layer

  6. Module 2 Lesson 2 • Symbolizing features based on attributes • Drawing features to show categories • Drawing features to show quantities • Display features with categories & quantities

  7. Categorical Quantities Quantities? Categories? • Data types: • Nominal • Ordinal • Interval • Ratio

  8. Module 2 Lesson 3 • Classifying data • Grouping attribute values into classes • Deciding which classification scheme to use • Explore methods of classifying data • (or – how to lie with maps!)

  9. Classify? • Place data into groups • 1 2 3 4 5 6 7 8 9 • 0 1 2 • By doing this you are saying that: • The differences between values within a group are not significant • Or • Even if they are I can’t display them effectively

  10. Purpose of Classification • The most important process involved in producing a choropleth map • Values are grouped into classes to simplify and generalize mapped patterns for the reader. • Although some details may be lost in classification, the results allow more information to be transmitted. • Minimize the differences within each class and maximize differences between classes. • The spatial pattern shown by choropleth map can be greatly altered by changing the classification method.

  11. Number of classes • The number of classes determines how detailed the mapped distribution will be. • The minimum number of classes is normally 4. • The maximum number is eleven (or 12). • The optimum number is 5 or 6. • On a monochromatic map (single color ramp) viewers cannot perceive more than 8 classes

  12. The Symbology Tab • There are actually several ways to classify the data • Natural breaks • Equal interval • Quantile • Manual • This can get quite messy • AND IT DOES NOT CHANGE THE DATA!

  13. Module 2 Lesson 4 • Mapping density and proportion • Mapping density using attribute values • Mapping density visually • Mapping proportion • Map density and attribute relationships

  14. So • There are 4 exercises • This is harder than Module 1 and you have to pay attention • But it is basic theory related to communicating with maps

  15. Overview • Introduction to module 2 • Concept of layers • Brewer’s on-line help • Examples

  16. Layers • A confusing term since it is used in several ways • GIS professionals have used the term to refer to the layers of data in the layered structure of gis data….

  17. Skewer oflocation Streams Power lines Landuse Roads Layers • A confusing term since it is used in several ways • GIS professionals have used the term to refer to the layers of data in the layered structure of gis data….

  18. Layers • A confusing term since it is used in several ways • GIS professionals have used the term to refer to the layers of data in the layered structure of gis data…. • It also has a very specific and important meaning in ArcGIS

  19. Layers in ArcGIS • When you create a symbology it is saved in the map document so that when you reopen the features have he same symbology • What if you would like to use the same symbology in different maps? • Layer Files to the rescue.

  20. Layer Files • Save the link to the data • And • The symbology used • Then you can add the layer file to any map using that data • If it can’t find the data it will not work!

  21. From Help • In ArcGIS, a reference to a data source, such as a shapefile, that defines how the data should be displayed on a map. • Layers can be stored in map documents (.mxd) or saved individually as layer files (.lyr). • Layers are conceptually similar to themes in ArcView 3.x that have legend files (.avl)

  22. Overview • Introduction to module 2 • Concept of layers • Classification • Brewer’s on-line help • Examples

  23. Overview • Introduction to module 2 • Concept of layers • Brewer’s on-line help • Examples

  24. Summary • ArcGIS, as you will see, contains hundreds of symbols for points and lines • And hundreds of outlines and fills for polys • Keeping track of where they are is a problem

  25. Summary • Classification is the trickiest part of this module • And probably the most important • So read and do the exercises carefully -- and keep notes • And, as usual, there are multiple ways of doing things

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