 | 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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