GIS (geographic information system)

1. vector data
1. Point Data -- layers described by points (or "event") described by x,y (lat,long; east, north)
2. Line/Polyline Data -- layers that are described by x,y points (nodes, events) and lines (arcs) between points (line segments and polylines)
3. Polygon Data -- layers of closed line segments enclosing areas that are described by attributes
   
   Polygon data can be "multipart" like the islands of the state of Hawaii.

2.  raster data (grids of numbers describing e.g., elevation, population, herbicide use, etc)
3. images or pictures such as remote sensing data or scans of maps or other photos.  This is special "grid" where the number in each cell describe what color to paint or the spectral character of the image in that cell. (to be used, the "picture" must be placed on a coordinate system, or "rectified" or "georeferenced")
4. TINs - Triangular Irregular Networks - used to discretize continus data
5. Terrain datasets built from lidar and other point clouds.

• age
• lithology
• percent quartz
• etc, for each rock type on the map.

• most GIS programs can either plot the polygon by the identifier or by one of the attributes
  
  

The above examples from the following project shows two ways to portray census data in Virginia. In the top image, each county/city gets a name and unique color , and in the bottom, the population density per square mile is read from the layer's attribute table and plotted using a different color for each class of density.

• metadata are the most forgotten data type
• absolutely necessary if you're going to use data, or if someone is going to use your data later (or your derivative information)
• contains information about
0. scale
1. accuracy
2. projection/datum
3. data source
4. manipulations
5. how to acquire data