What is GIS?

GIS stands for Geographic Information Systems, often defined as a computerized database management system for capture, storage, retrieval, analysis, and display of spatial data. Any data that includes information about location—be it a street address, zip code, census tract, or longitude and latitude coordinates—can be considered spatial. Many different types of data can be integrated into GIS and represented as a map layer. When these layers are drawn on top of each other, spatial patterns and relationships often emerge. The most common GIS product is a map, but GIS can be used to generate answers to queries or as part of spatial statistical analysis.

GIS also stands for Geographic Information Science, an emerging interdisciplinary field that combines elements of geography, cartography, and computer science. Thought of in this way, GIS is a way of thinking about the world that puts spatial relationships at the center. GIS technology was originally developed to model the natural world—landmasses and bodies of water, elevation, temperature, soil composition, and suitable habitats for animals. More recently, social scientists have begun applying these tools—and this way of thinking—to understanding the social and built environment.

Overview of different formats of spatial data:
Raster and Vector

GIS stores and supports two major categories of data formatting: Raster and Vector. Vector data represents objects based on distinct points, line or areas described by their x and y coordinates and their topological relations to each other. On the other hand continuous surfaces can be better represented using raster data which are a combination of cells which have values representing the landscape.

Raster versus Vector Data





GIS Resources on the Web

Data Sources:
Dictionary of GIS Terms

National Spatial Data Clearinghouse
Geography Network
GIS Data Depot

Open GIS Consortium
American Congress on Surveying and Mapping
National States Geographic Information Council
University Consortium for Geographic Information Science California Geographic Information Association

Other Online GIS Applications:
Neighborhood Knowledge Los Angeles
Baltimore Neighborhood Indicators Alliance
Vallejo Economic Development Information System
Nashville Metropolitan Planning Department
Map Milwaukee

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