W F 3: Shuurman: Chp. 4-5

GIS is useful to discern more information than is possible from raw data.

Often used to determine if a certain point is located within an area.

Overlay analysis is a common technique in GIS.  You must be aware of scale when doing this, and make sure that the scales are compatible.

• Buffering extends overlay analysis to include areas that are affected as well as the designated zones in question.

Set theory uses the areas/spatial entities that are the basis of GIS to express relationships between them.

• Map algebra extends the utility of set theory.  It adds, subtracts, multiplies, and divides spatial areas.
• Map algebra can be used to reclassify attribute values for spatial areas.

Reclassification is a very important technique in GIS.  It allows the generation of new values for spatial areas without changing the definition of spatial units.

• Reclassification is useful to divide values into categories (eg. economical, affordable, and luxury houses).

Key point: GIS uses models to represent the world.  While these models do not accurately reflect reality, they are a way to represent things in a way we can understand and in a way that is useful (“all models are wrong, but some are useful”).

Multiple-criteria evaluation allows you to combine several attributes in order to determine the suitability of an area.

• This allows multiple perspectives to be considered.
• Analysis will vary depending on how the attributes are ranked in relation to each other.

Key point:  Models and the criteria that are chosen always reflect an agenda.

Key point: Context and frame of reference contribute to the legitimacy of any system of representation (p. 129).

Summary of GISystems and GIScience:  Systems refers to the “doing” of GIS (software and hardware), while science refers to the theory and intellectual assumptions behind it.

Key point:  Maps created with GIS are NOT simple, definitive statements about spatial relations.  They are representations of a particular point of view.  GIS should be used not to simply make map-pictures, but to represent and predict spatial phenomena (p. 148).

Key point:  GIS software programs are only as good as the people who use them.  The program will still give an analysis even if you give it poorly conceived data.  You must be educated about the proper use of GIS.