Definitions of GIS Works with geographic information Performs

Definitions of GIS • Works with geographic information • Performs data input, management, manipulation/analysis, and output functions • Composed of hardware, software, people, and institutional context

Definitions of GIS • Primary related technologies – computer cartography – database management (information technology) – computer graphics – remote sensing – computer aided design (CAD)

Why use GIS? • GIS provides – data integration and standardization – methods for managing large volumes of data – advanced spatial analysis capabilities – automation of repetitive tasks – sophisticated means of communication: distribution and output

Applications of GIS Four basic categories: – environmental/natural resource management – urban and regional management – infrastructure management – commercial

Ways of storing digital data • File structures – simple – ordered sequential – indexed • Databases and data models – hierarchical – network – relational

Relational data model Student ID Last First Grade Class 1 Wood Bob C Geog 357 2 Kent Chuck B Geog 115 3 Smith Jane A Geog 357 4 Boone Dan B Geog 357 Class Name #Stud Instructor Geog 20 120 Brower Geog 115 120 Mennis Geog 357 48 Mennis Instructor Name Office Mennis 332 Brower 517

Spatial Data Representation Conceptual Model Data Modeling Levels Data Model Data Structure File Structure

Spatial Data Representation • Can distinguish between two different conceptualizations of geographic phenomena: – object view: empty space ‘littered’ with objects (e. g. lakes) – field view: a geographic entity that ‘varies’ across a space (e. g. elevation)

Spatial Concepts • Mathematical Types of Space – Euclidean – Network – Metric – Topologic

Spatial data models • Raster – exhaustive regular or irregular partitioning of space – associated with the field view – location-based • Vector – points, lines, areas – associated with the object view – object-based

Vector data model • TIN: Triangulated Irregular Network

Vector data input and editing Digitizing Process: • • prepare map sheet digitize the coverage identify and correct digitizing errors build topology identify and correct topology errors assign attributes identify and correct attribute errors

Raster data models • A raster representation is composed a series of layers, each with a theme

Raster data models • Compression of raster data: – run length encoding – value point encoding – chain codes – block codes – quadtrees