map basics geog 370 christine erlien, instructor
TRANSCRIPT
![Page 1: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/1.jpg)
Map Basics
GEOG 370
Christine Erlien, Instructor
![Page 2: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/2.jpg)
Map Basics Maps as a language
– Symbolization
– Scale
– Simplification/generalization
– Grid systems
– Projections
![Page 3: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/3.jpg)
Value of Maps
Way to record & store information
Way to analyze locational distributions & spatial patterns
Method of presenting information & communicating findings
![Page 4: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/4.jpg)
Value of Maps
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![Page 5: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/5.jpg)
![Page 6: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/6.jpg)
Graphicacy Understanding graphic devices of
communication– Maps– Charts– Diagrams
Why? – Understanding usage of graphic devices
increases our abilities• Describing spatial phenomena • Making decisions
![Page 7: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/7.jpg)
Maps Model of reality, not a miniature version
Media for delivering geographic information
Target audience determines level of abstraction, map scale, symbology
![Page 8: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/8.jpg)
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
![Page 9: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/9.jpg)
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:
![Page 10: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/10.jpg)
Selection
Classification
Simplification
Symbolization
Cartographic abstraction & generalization
![Page 11: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/11.jpg)
Selection Decisions about
– Area to be mapped
– Map scale
– Map projection
– Data variables
– Data gathering/sampling
![Page 12: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/12.jpg)
Classification
Organizes mapped information
Qualitative or quantitative– Qualitative: Spatial distribution of nominal
or ordinal data
– Quantitative: Spatial aspects of numerical data
![Page 13: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/13.jpg)
Classification of interval/ratio data
Dividing data into categories– Natural breaks
– Quantile breaks
– Equal intervals
– Standard deviation
![Page 14: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/14.jpg)
Natural breaks– Imposed
• Fractions/multiples of mean income levels• Rainfall thresholds that support different
vegetation types (e.g., arid, temperate)
– Calculated by software
Classification of interval/ratio data
![Page 15: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/15.jpg)
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
Classification of interval/ratio data
![Page 16: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/16.jpg)
Classification of interval/ratio data
Equal intervals – Range between lowest & highest values
divided equally among the number of classes
![Page 17: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/17.jpg)
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
![Page 18: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/18.jpg)
From Longley et al. Geographic Information Systems and Science
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Generalizing features
From How To Lie with Maps, M. Monmonier
![Page 20: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/20.jpg)
Symbolization
http://www.colorado.edu/geography/gcraft/notes/cartocom/cartocom_f.html
![Page 21: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/21.jpg)
Map Types Reference maps
– Require conformity to standards
– Examples: USGS topographic maps, navigation charts
Thematic maps– Cartographer has control over map design
– Ex: Spatial distribution of variable
![Page 22: Map Basics GEOG 370 Christine Erlien, Instructor](https://reader034.vdocuments.mx/reader034/viewer/2022051401/5697bf781a28abf838c819fd/html5/thumbnails/22.jpg)
Thematic map types: Dot distribution
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?
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http://www.unl.edu/nac/conservation/atlas/Map_Html/Demographics/National/Minority_Operated_Farms/1997.htm
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http://www.cdc.gov/hiv/graphics/images/dotmaps/83aids.htm
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Dot distribution: nominal point symbols
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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
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Thematic map types: Proportional dot
http://goliath.frostburg.edu/rpotts0/ProportionalCircleMapB.jpg
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Thematic map types: Ordinal line
http://clerk.ci.seattle.wa.us/~ordpics/115137At10TRFigA4.gif
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Thematic map types: Ordinal area
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Thematic Map Types: Choropleth 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
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http://personal.uncc.edu/lagaro/cwg/color/Choropleth-5Good.gif
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Principles of map design
Visual variables
– Jacques Bertin, 1967
– System for representing information based on the visual properties & arrangement of graphic symbols
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Bertin’s visual variables
Hue: Colors perceived
Value: Lightness/darkness
Saturation: Intensity/purity
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Major Map Elements
Necessary components of a typical map– Title
– Legend: Interpretive key to symbols • Symbols: Used to describe features
– Scale bar
– North arrow
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Major Map Elements
Necessary components of a typical map– Projection
– Cartographer
– Date of production
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Map Elements Some elements are used to selectively assist
effective communication– Neatlines: Used to frame map
– Inset maps: Close-up view
– Charts
– Additional text
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Legend
Scale
Credits
North ArrowPlace nameInset
Ground
Figure
Neat lineBorder
Title
Map Elements
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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
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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
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Methods of illustrating map scale
Graphic scale– Measured ground distances appear on
map– Change with changes in scale of output
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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