1. GEOG 370 Christine Erlien, Instructor
Map Basics
GEOG 370
Christine Erlien, Instructor

2. Map Basics Maps as a language Symbolization Scale
Simplification/generalization
Grid systems
Projections

3. Value of Maps Way to record & store information
Way to analyze locational distributions & spatial patterns
Method of presenting information & communicating findings

4. Value of Maps

6. Graphicacy Understanding graphic devices of communication Why? Maps
Charts
Diagrams
Why?
Understanding usage of graphic devices increases our abilities
Describing spatial phenomena
Making decisions

7. Maps Model of reality, not a miniature version
Media for delivering geographic information
Target audience determines level of abstraction, map scale, symbology

8. Maps as Models: A paradigm shift in cartography
Communication paradigm -> analytical paradigm
Communication paradigm
Traditional approach to mapping
Map itself was a final product
Communication tool
Limits access to original (raw) data

9. Maps as Models: A paradigm shift in cartography
Analytical paradigm
Maintains raw data in computer
Display is based on user’s needs
Transition ~ early ’60s
Advantage:

10. Cartographic abstraction & generalization
Selection
Classification
Simplification
Symbolization

11. Selection Decisions about Area to be mapped Map scale Map projection
Data variables
Data gathering/sampling

12. Classification Organizes mapped information
Qualitative or quantitative
Qualitative: Spatial distribution of nominal or ordinal data
Quantitative: Spatial aspects of numerical data

13. Classification of interval/ratio data
Dividing data into categories
Natural breaks
Quantile breaks
Equal intervals
Standard deviation

14. Classification of interval/ratio data
Natural breaks
Imposed
Fractions/multiples of mean income levels
Rainfall thresholds that support different vegetation types (e.g., arid, temperate)
Calculated by software

15. Classification of interval/ratio data
Quantile breaks
Predetermined number of classes
Equal # observations in each class
5 classes: good for uniform distributions
Limitation: Potentially misleading
Numeric size of each class rigid 
Numerically similar values may be in different classes
Wide-ranging values may be in same class

16. Classification of interval/ratio data
Equal intervals
Range between lowest & highest values divided equally among the number of classes

17. Classification of interval/ratio data
Standard deviation
Distance of observation from mean
GIS calculates mean value & generates class breaks in s.d. measures above & below
Using 2-color ramp helps emphasize values

18. From Longley et al. Geographic Information Systems and Science

19. Generalizing features
From How To Lie with Maps, M. Monmonier

20. Symbolization

21. Map Types Reference maps Thematic maps Require conformity to standards
Examples: USGS topographic maps, navigation charts
Thematic maps
Cartographer has control over map design
Ex: Spatial distribution of variable

22. Thematic map types: Dot distribution
Dots, other small point symbols
Dot will represent a set number of a particular feature
If nominal symbols are used, will not vary in size. Why?

25. Dot distribution: nominal point symbols

26. Thematic Map Types: Prop. symbol
Proportional Symbol
Graduated point, ordinal line symbol
Size of symbol proportional to size of data value
For areas  color, pattern

27. Thematic map types: Proportional dot

28. Thematic map types: Ordinal line

29. Thematic map types: Ordinal area

30. Thematic Map Types: Choropleth
Subdivisions are preexisting units
Example: Census tracts; county, state, national boundaries
Average value for areal unit is calculated & symbolized
Generally ratio values
Example: Population density, yield/acre, average income

32. Principles of map design
Visual variables
Jacques Bertin, 1967
System for representing information based on the visual properties & arrangement of graphic symbols

33. Bertin’s visual variables
Hue: Colors perceived
Value: Lightness/darkness
Saturation: Intensity/purity

34. Major Map Elements Necessary components of a typical map Title
Legend: Interpretive key to symbols
Symbols: Used to describe features
Scale bar
North arrow

35. Major Map Elements Necessary components of a typical map Projection
Cartographer
Date of production

36. Map Elements
Some elements are used to selectively assist effective communication
Neatlines: Used to frame map
Inset maps: Close-up view
Charts
Additional text
Note – when might an inset be necessary
Example: when mapping the U.S., useful to put Alaska & Hawaii in inset
Example: helpful when observations/data are clustered in a small section of the map

37. Map Elements Legend Scale Credits North Arrow Place name Inset Ground
Figure
Neat line
Border
Title
Figure: The area of interest (area being mapped)
Ground: background

38. Map Scale Map scale: Ratio between map distance & ground distance
large scale map vs. small scale map
1:250,000 > 1:1,000,000
Large scale map  more details
Scale-dependent map display in GIS
Minimum vs. Maximum map scale

39. Methods of illustrating map scale
Verbal scale
Example: 1 inch equals 63,360 inches
Easily understood
Representative fraction scale
Example: 1:250,000
No units necessary  map & ground distance in same units as fraction
63360 inches=5280 ft=mile

40. Methods of illustrating map scale
Graphic scale
Measured ground distances appear on map
Change with changes in scale of output

41. Map scale vs. scale generally
Large scale study vs. small scale study
Large scale study
Extensive in scope or scale
Small scale study
Small area or limited scope
In which study scenario will data be collected in more detail?
In the sense it is being used here  opposite the meaning of scale in map scale