2017-11-27 1 Geography 38/42:286 GIS 1 Topic 10: Other Thematic Mapping Techniques 1 What is an Isarithmic Map? Portrays continuous surfaces using isolines Represent constant value Located with reference to control points Surface may be: real (e.g. a topographic, or barometric surface) or conceptual (e.g. population or tortoise density) 2 When Is It Used? Feature to be mapped is continuous in nature Or can be visualized as a surface 3
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Topic 10: Other Thematic Mapping Techniques · 2017-11-27 1 Geography 38/42:286 GIS 1 Topic 10: Other Thematic Mapping Techniques 1 What is an Isarithmic Map? Portrays continuous
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2017-11-27
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Geography 38/42:286
GIS 1
Topic 10:
Other Thematic Mapping Techniques
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What is an Isarithmic Map?
Portrays continuous surfaces using isolines
Represent constant value
Located with reference to control points
Surface may be:
real (e.g. a topographic, or barometric surface)
or conceptual (e.g. population or tortoise density)
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When Is It Used?
Feature to be mapped is continuous in nature
Or can be visualized as a surface
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Spatial Data Characteristics
Two types of isarithmic maps
Different spatial data characteristics
Isometric
Isoplethic
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Asaptial Data Characteristics
For Isometric form:
Raw or derived values may be used:
For Isoplethic form:
Derived values used; never raw values
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Other Considerations
Legend design
Ancillary information, base map info
Line symbols and labels
Map projection
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What is Flow Mapping?
Depicts movement of phenomena
Uses line symbols of varying type/width
May indicate direction with arrows
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When Is It Used?
Only option when objective is to show:
movement/flow
spatial interaction/connectivity
Can show more than one phenomena
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Types of Flow Maps
Qualitative
Flow of different types of objects
Quantitative
Flow of different quantities of objects
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Flow Line Placement
Line symbols may:
Show actual path
Stylized path
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Actual Flow Paths
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Stylized Flow Paths
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Spatial Data Characteristics
Can be used to map flow:
Between discrete point locations
Between discrete areal units
Along discrete line features
for attributes (things) that flow/move
Not continuously distributed phenomena
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Aspatial Data Characteristics
Depict raw data values only
Derived data do not flow
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Types of Flow Maps
Variations based on direction and pattern of flow
Radial Multiple sources to/from a central location; 1-way flow
Distributive Multiple sources to multiple destinations; 1-way flow