| Term | Definition |
|---|
| Tobler's First Law of Geography | Everything is related to everything else, but near things are more related than distant things |
| data model | structures & rules that are programmed into a GIS to accomodate data |
| digital | from "digits" for fingers which represents counting system based on ten unique symbols 0-9 |
| binary | a system of counting based on 2 unique symbes |
| key GIS representation issues | what to representa and how to represent it |
| atomic elements | facts about the geographic world |
| types of attributes | nominal, ordinal, interval, ratial, cyclic |
| nominal attribute | simplest, serves only to identify or distinguish one entity from another (placenames) |
| ordinal attribute | values have a natural order (soil quality) |
| interval attribute | where the differences between values makes sense (scale of Celsius) |
| ratio attribute | ratios between values makes sense such as weight scales |
| cyclic attribute | data which is directional such as compass headings |
| discrete object view | well defined boundries |
| object types | points, line, polygons |
| continuous field view | attribute defined at every point |
| field value types | vector, raster |
| vector representation | all lines are captured as points connected by precisely straight lines |
| raster representation | space divided into an array of rectangular cells |
| scale types | Digital Raster Graphic (DRG), Digital Line Graphic (DLG) |
| digital raster graphic | map is scanned at a very high density, using very small pixels, so the raster looks very much like the original |
| digital line graphic | every geographic feature shown on the map is represented as a point, polyline, or polygon |
| methods of generalization | simplification, smoothing, aggregation, amalgamation, merging, collapse, refinement, exaggeration, enhancement, displacement |
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