Map is a subcategory of visualization. (although it originated mostly out of navigation purposes.)

Since geospatial information is mostly 2-dimensional and inherently 3-dimensional, maps stands out as a distinctive approach to visualization. To add attributes to maps, varying point size, line width, and color shades are used instead of length/height. Different attributes can be layered over each other for spatial correlation and pattern seeking.

Advanced extensions of maps include interactive feature, 3-D plot of density or time series, and animation. These extensions present quantities more acurately, and incorporates the time scale.

GIS Database Components:

  1. Spatially Referenced Data
    • Raster (Thematic Data: Digital Elevation Model (DEM), Imagery: Aerial and Satellite)
    • Vector (Point, Polyline, Polygon)
  2. Attribute Tables (metadata)

Elements of a map:

  1. Base map [label]
  2. Overlay maps (Layers):
    1. geometries [semi-transparent overlay, legend]
    2. Metadata/attributes associated with each geometry

Types of Maps

  • Descriptive:
    • points - scatterplot: store locations, etc.
    • lines - roads, mains, sewer, cables, etc.
    • area - categorical map: transportation access area, flood-prone area, land-use zoning, climatic regions, etc.
  • Quantitative:
    • points - bubble plot: adolescent fertility rate, etc.
    • lines - lines w varing width/color: traffic speed, main capacity, etc.
    • area - choropleth: unemployment rate, access to improved water source, etc.
  • Extensions:
    • 3D bar chart: population density, crime rate time series
    • animation: traffic flow, population growth

Note: [basics - derivatives: application]

Thematic Mapping

Thematic map is a type of map especially designed to show a particular aspect (theme) connected with a specific geographic area.

Major thematic mapping techniques:

  1. Dot Distribution Map: dot for presence at a location
    • Proportional Symbol: symbols of different sizes on regions/locations
  2. Choropleth Map: coloring (gradation) or shading of regions
    • Dasymetric Map: choropleth map with internal distribution modeled from ancillary information, e.g. using area to calculate density.
  3. Isopleth Map: isolines (contour) of a smooth continuous attribute

3D Views

🏷 Category=Geographic Information System