1. Lecture 02 The Basics pf Creating a GIS Map
GTECH 361
Lecture 02 The Basics pf Creating a GIS Map

2. Today’s Content
Techniques for choosing and modifying symbols and text

3. Today’s Objectives
choose symbols for point, line, and polygon features
modify symbol properties such as color, size, and outline
label map features using an attribute and by adding text
symbolize features to show type, rank, or amount
group features into classes and apply symbols to each class
compare different methods of grouping features into classes
correct visual distortion caused by differences in area
show proportional amounts on a map by normalizing data
symbolize features to show density

4. Two Map Categories
Reference Maps
Multi purpose
Thematic Maps

5. Effective Symbolization
Pictorial symbols a picture says more than a 1,000 words

6. Types of Symbols Point Line Polygon Marker Symbol Color Size Angle
Line symbol
Polygon
Fill color
Fill pattern
Outline color
Size
Angle
Width
Outline width
Background color

7. Symbol Sets ArcGIS comes with 25 off the shelf
You can create or import your own
Similar symbols in vastly different symbol sets, e.g.,

8. Labeling (Map) Features
Retrieving label value from field value in the feature’s attribute data

9. Label vs. Annotation
Manually adding a label describing a map feature that has representation in the underlying dataset
Dynamic labels are context-dependent

10. Representing Attribute Values
All features of a layer are the same
Differentiation according to feature’s attribute value

11. Representing Categories

12. Representing Quantities

13. Classifying Data Three decision prior to classification
How many classes?
What method to use for placing the values into classes?
What kind of symbology?

14. Classification Methods
Natural breaks
Equal interval
Quantile
Manual

15. How to Decide (on a classification scheme)
Rule of thumb: classes
Classification histogram

16. Classification method How many classes to have
How to Decide, part II
Classification method
When to use
How many classes to have
Natural breaks
When attributes are distributed unevenly across the overall range of values
Look for natural groups
Equal interval
When you want all classes to have the same range
Easily understood interval, such as 2, 50, 1000, etc.
Quantile
When attributes are distributed in a linear fashion
Determined by purpose of the map
Manual
When you want classes to break at specific values

17. Proportional Symbology
Absolute quantities can be misleading
When quantities vary a lot
When size of geographic feature varies a lot
Solutions
Mapping density
Mapping proportion

18. Normalization
Divide value of an attribute by value of another attribute
Most commonly by area resulting in density
Already normalized data should not be normalized by yet another attribute

19. Dot Density Maps Each dot represents a specific amount
Dots map randomly within each polygon
Individual dots in a dot density map are not associated with actual location coordinates

20. Common reasons to map attribute relationships
Mapping Proportion
Common reasons to map attribute relationships
What to map
Example
Proportion of the part to the whole
Countries: Bushels of wheat exported normalized by bushels of wheat harvested
Rate of something
Counties: Cases of heart disease normalized by total population
Relationship of one characteristic to another
Schools: Number of students normalized by the number of teachers
Relationship of one time period to another
Sales territories: Last year's sales revenue normalized by this year's sales revenue

21. Representing Proportions
Ratios between 0 and 1
Percentages (ratios multiplied by 100)
Rates based on a round number
Per person
Per 100
Per 1,000