Final Review Session; Geography 258
Second half of class based on lectures 14-26, refer to first half for the whole story
Overall Objectives:
- Continuing to study Geographic Information as represented
on maps
- Geographic Information Systems (GIS)
- Judgements about fitness for use
List of lab procedures:
- Lab 6: thematic mapping sites
- Lab 7: GIS Analysis
- Reports on sources
Thematic Mapping
Choropleth procedures
- Classification (examples: equal intervals, quantiles)
- Classed values presented as ordered by use of Color
(Value dark-light; Hue ramps; Saturation)
- Limitations of area-based attributes (standardizing by ratios-
Derived Values; per capita, per area density, etc.)
Proportional Symbols
- Don't classify, Use SIZE, Based on point locations...
Many more kinds: dot density, etc.
Bottom line: depends on levels of measurement (kinds
of attributes) and graphic variables (symbol set)
GIS Operations
Concept of layers: based on map reproduction, taken
further as database organization
Overlay
- brings attributes together that did not come from the same
set of geometric objects
- Procedures to combine attibutes:
- logical combinations: AND (needs both); OR (needs either
one)
- rankings: more preferred, less preferred
- explicit trade-offs: weighted scores, etc.
- Depends on common spatial reference system (coordinates,
projection, datum; see lecture 10)
Buffers
create new geometry: convert lines to areas.
GIS Transformations
- Data sources are rarely in the form you want them.
- Transformations convert by use of neighborhoods (spatial
part) and attribute combination rules.
Bottom line: depends on how the data are acquired (measurement
framework) and represented (data structure)
Accuracy and Fitness for Use
Components of Data Quality
(beyond just "accuracy" and the old National Map
Accuracy Standard)
- Lineage
- Positional Accuracy
- Attribute Acuracy
- Logical Consistency
- Completeness
Bottom line: user is responsible to figure out if the
source is sutiable for the purpose.
Version of 10 March 2000