Introducing Geographic Information Systems with ArcGIS: A Workbook Approach to Learning GIS, 3rd Edition

Spatial Data for Decision Making

We have said spatial data relate to conditions, facts, and objects in three-dimensional space. Most spatial data that now exist use a two-dimensional referencing scheme such as latitude/longitude (or projections thereof) or street addresses. Unless the dataset is specifically one that considers the matter of altitude, this third coordinate is either included as part of the attribute data (rather than part of the locational identifier) or is implied by the nature of the data. For example, if the data describe soil characteristics, one understands that the top few feet of the Earth’s crust, regardless of altitude, are being described.

Data types that might be part of spatial datasets are exemplified in Table 2-1.

TABLE 2-1 Example Data Types Included in Spatial Data

Soils	Types, physical and chemical properties
Vegetation	Species composition, age
Wildlife habitat	Types, carrying capacity
Hydrology	Ground and surface water, volume, flows
Geology	Rock types, minerals and ores, physical and chemical properties, oil and gas deposits
Physiography	Elevation, slope, aspect
Land use	Activity types, structure types, zoning
Land cover	Types, facts about what covers the surface
Transportation facilities	Types, capacity, schedules, condition, age
Utility distribution systems	Service areas, capacity, historical features and landmarks—importance, condition, ownership, use
Census districts	Population, housing, other demographic information ...