Data Types and Models

Data Types

Geography data comes in three basic forms:

Map data. Map data contains the location and shape of geographic features. Maps use three basic shapes to present real-world features: points, lines, and areas (called polygons). Learn more.

Attribute data. Attribute (tabular) data is the descriptive data that GIS links to map features. Attribute data is collected and compiled for specific areas like states, census tracts, cities, and so on and often comes packaged with map data. When implementing a GIS, the most common sources of attribute data are your own organization's databases combined with data sets you buy or acquire from other sources to fill in gaps.

Image data. Image data ranges from satellite images and aerial photographs to scanned maps (maps that have been converted from printed to digital format). Learn more.

Data Models

Data models are the rules the GIS follows, such as "county lines do not overlap," and are essential for defining what is in the GIS as well as supporting the use of GIS software. All spatial data models fall into two basic categories:

Vector data model. Discrete features, such as customer locations and data summarized by area, are usually represented using the vector model. Learn more.

Raster data model. Continuous numeric values, such as elevation, and continuous categories, such as vegetation types, are represented using the raster model. Learn more.

Raster or Vector?

While any feature type can be represented using either model, discrete features, such as customer locations, pole locations or others; and data summarized by area, such as postal code areas or lakes; are usually represented using the vector model. Continuous categories, such as soil type, rainfall, or elevation, are usually represented using the raster model.

This map shows vector data (the streets) laid on top of raster data (the mountains and valley floor).