GTECH 709 GIS Data Formats GIS hierarchies GIS

GTECH 709 GIS Data Formats GIS hierarchies GIS data models Vector model Raster model GIS data formats

GTECH 709 GIS hierarchies Chrisman’s spheres ANSI SPARC model Levels of modeling

Chrisman’s Spheres

ANSI-SPARC Model for Software Development GIS are systems to model the world User Model Conceptual Model Operational Model

GIS Are Systems to Model the World User Model – how we intuitively think Conceptual Model Operational Model ANSI-SPARC Model for software development

GIS Are Systems to Model the World User Model Conceptual Model how we systematically define ideas Operational Model ANSI-SPARC Model for software development

GIS Are Systems to Model the World User Model Conceptual Model Operational Model how we fuse systematic thinking into a technologically defined context

The ANSI/SPARC Model and Chrisman’s Spheres application disciplines context discipline spatial modeling geoinformation theory conceptual modeling logical data modeling physical data modeling OPERATIONAL computer science

GTECH 709 GIS data models Digital maps as models GIS data models

Digital Maps as Models • Representing a complex reality • Continuous variation • Spatial Data: spatial, temporal and thematic Geography = ƒ ( space, time, attributes) • Data models

Digital Maps as Models • Raster Model - The world as regular tessellations defined by areal property • Vector Model - The world as points, lines, areas and attributes…. . making objects • Object Model - The world as interacting entities with spatial dimensions

GTECH 709 Vector data models Spaghetti vs topological models Vector model details Topology

Vector Data Models • Spaghetti model A file of spatial data that is a just a collection of co-ordinate strings. Each entity (or piece of spaghetti) is represented by one data entry. There is no topology. • Topological models Topology refers to the spatial relationships between objects. The topological model represents spatial relationships such as: length, area, connectivity, contiguity

The Vector Data Model

Vector Details • Nodes • Arcs • Polygons

Topology • Maintaining spatial relationships

Topology (2)

GTECH 709 The raster model Raster components Discrete vs. continuous

Raster Data Model

Cell

Column Row

Cell With Value

Zones

No Data

Raster Attribute Table

Coordinate Space and the Raster Dataset

Discrete vs. Continuous

Resolution

Imagery

GTECH 709 GIS data formats Shapefiles Geodatabases Coverages

GIS Data Formats

Shapefiles

(ESRI) Geodatabase

Organizing Vector Data • All features in a feature class have the same geometry type, the same attributes, and are located within a common geographic extent

Coverages • In Arc. GIS • In MS Explorer