Hey what the hell is GIS anyway!?

GIS stands for Geographic Information Systems. Geographic Information Systems is a combination of elements designed to store, retrieve, manipulate, and display geographic data - information about places. It is a package consisting of four basic parts: hardware, software, data and a thinking operator. GIS can run on robust comptuer technology, capable of processing millions of computations per second. ArcView runs on Macintosh, PC and UNIX systems. Or GIS can be run on older platforms using such as DOS.

Software such as ESRI's ArcView GIS software provides the mechanism for analyzing relationships between geographic entities, and allows the explorer to interact with dynamic maps on the computer screen. The software also permits the user to produce high-quality maps on a variety of output devices. ESRI is the not the only one out there. Clark Lab's IDRISI software, SmallWorld, MapInfo, ERDAS, ect or just a few other GIS type software out there.

Data in a GIS comes in two parts: 1) the geographic data that represents the physical places: cities, rivers, lakes; and 2) the attribute data that describes the characteristics of the geographic features: population, length, area. Matching each unique geographic feature with its corresponding attributes is the true power behind GIS.

Spatial features are stored in a coordinate system (latitude/longitude, state plane, UTM, etc.), which references a particular place on the earth. Descriptive attributes in tabular form are associated with spatial features. Spatial data and associated attributes in the same coordinate system can then be layered together for mapping and analysis. GIS can be used for scientific investigations, resource management, and development planning.

All spatial data is geographically referenced to a map projection in an earth coordinate system. For the most part, spatial data can be "re-projected" from one coordinate system into another, thus data from various sources can be brought together into a common database and integrated using GIS software. Boundaries of spatial features should "register" or align properly when re-projected into the same coordinate system. Another property of a GIS database is that it has "topology," which defines the spatial relationships between features. The fundamental components of spatial data in a GIS are points, lines (arcs), and polygons. When topological relationships exist, you can perform analyses, such as modeling the flow through connecting lines in a network, combining adjacent polygons that have similar characteristics, and overlaying geographic features.

- Extracted from the USGS Website

United States Geological Survey GIS
Enviromental Systems Reasearch Institute ESRI
Clark Lab's IDRISI
SmallWorld GIS
MapInfo
ERDAS

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