GIS Data Types

GIS technology utilizes two basic types of data 1. Spatial Data Describes the absolute and relative location of geographic features.

GIS Data Types 2. Attribute Data/Tabular Data Describes characteristics of the spatial features. These characteristics can be quantitative or qualitative in nature.

GIS Data Types Data Layers Are the result of combining spatial and attribute data. Essentially adding the attribute database to the spatial location.

Other Data Types Images and Multimedia data are becoming more prevalent with changing technology. Image: e.g. photographs, animation, movies, etc. Attribute: e.g. sound, descriptions, narration’s, etc.

Spatial Data Models Traditionally spatial data is stored and presented in the form of a maps. Three basic types of spatial data models have evolved for storing geographic data digitally. 1.Vector 2.Raster 3.Image.

Diagram reflects the two primary Spatial Data encoding techniques. Vector and Raster. Image data utilizes techniques very similar to raster data, however typically lacks the internal formats required for analysis and modeling of the data. Images reflects pictures or photographs of the landscape. 1. Vector Data Models

Vector data is characterized by the use of sequential points or vertices to define a linear segment. Each vertex consists of an X coordinate and a Y coordinate. Vector lines are often referred to as arcs and consist of a string of vertices terminated by a node.”A node is defined as a vertex that starts or ends an arc segment.”

1. Vector Data Models

1.Point Features are defined by one coordinate pair, a vertex.

1. Vector Data Models 2.Line Features is defined by a sequence of coordinate pairs defining the points through which line is drawn. 3.Polygonal Features are defined by a set of closed coordinate pairs.

1. Vector Data Models The topologic data structure is referred to as an intelligent data structure because spatial relationships between geographic features are easily derived. Many of the complex data analysis functions cannot effectively be undertaken without a topologic vector data structure.

1. Vector Data Models Topology is the critical element that distinguishes a GIS from a graphics or automated cartography system.

1. Vector Data Models The secondary vector data structure that is common among GIS software is the Computer Aided Drafting (CAD) Data Structure. It consists of strings of vertices, to define geographic features, e.g. points, lines, or areas. There is considerable redundancy with this data model since the boundary segment between two polygons can be stored twice, once for each feature. The CAD vector model lacks the definition of spatial relationships between features.

Vector Based Softwares GIS software programs are usually either vector or raster based with capabilities in using both layer types. ArcView ArcGIS ArcMap Geomedia MapInfo