Map Abstraction and Generalization

Study Notes

Map abstraction is the process of moving from the "real world" to the world of maps
Map content and shape vary according to purpose, need, and resources
Map generalization is the process of reducing the amount of detail in a map or database in a meaningful way
Generalization examples:
- Topographic map 1:10,000 vs. 1:50,000
- The relation between scale and generalization: as scale decreases, detail increases, and as scale increases, area decreases
- Scale 1:10,000 = 1 cm = 100 meters, Scale 1:50,000 = 1 cm = 500 meters, etc.

Map scale:
- Ratio of the distance on a map to the actual distance on the ground
- Example: 25,000:1, where 1 cm on a map is 25,000 cm in real life
Types of map scales:
- Bar scale (visual guide)
- Lexical scale (gives distance conversion in words)

Coordinate systems:
- A set of numbers used to determine position on the surface of the earth
- Geographic coordinate system (GCS) uses latitude and longitude to specify locations
GCS parts:
- Latitude: defines how far north or south a point is on the globe relative to the equator (0° to 90°)
- Longitude: defines how far east or west a point is on the globe relative to the prime meridian (0° to 180°)

Map projections:
- Methods and procedures used to transform the spherical 3D earth into 2D planar surfaces (e.g., paper maps, computer monitors)
- Mathematical formulas used to translate latitude and longitude on the earth to x and y coordinates on a plane
Map projection surfaces:
- Plane surface
- Cone surface
- Cylinder surface

Layers in GIS:
- Two types of data: raster and vector
- Raster: organized as cells arranged in rows and columns
- Vector: uses points, lines, and polygons
Data layers in GIS:
- Represent data in layers

Map anatomy:
- The study of the structure and components of maps
- Objectives: to understand maps, map types, map scale, coordinate systems, and map projections
Maps and map types:
- Maps can be stored in our brain (mental maps)
- Maps can be printed on paper
- Maps can appear online
Map types:
- Three types: reference maps, thematic maps, and others