What is GIS?

A GIS is mapping software that links information about where things are with information about what things are like. Unlike with a paper map, where "what you see is what you get," a GIS map can combine many layers of information. 

To use a paper map, all you do is unfold it. Spread out before you is a representation of cities and roads, mountains and rivers, railroads and political boundaries. The cities are represented by little dots or circles, the roads by black lines, the mountain peaks by tiny triangles, and the lakes by small blue areas. 

As on the paper map, a digital map created by GIS will have dots, or points, that represent features on the map such as cities; lines that represent features such as roads; and small areas that represent features such as lakes. 

The difference is that this information comes from a database and is shown only if the user chooses to show it. The database stores where the point is located, how long the road is, and even how many square miles a lake occupies. 

Each piece of information in the map sits on a layer, and the users turn on or off the layers according to their needs. One layer could be made up of all the roads in an area. Another could represent all the lakes in the same area. Yet another could represent all the cities.

Why is this layering so important? The power of a GIS over paper maps is your ability to select the information you need to see according to what goal you are trying to achieve.

A business person trying to map customers in a particular city will want to see very different information than a water engineer who wants to see the water pipelines for the same city. Both may start with a common map—a street and neighborhood map of the city—but the information they add to that map will differ. 

(Graphic image supplied courtesy of ESRI) 

How To Use GIS

Mapping where things are lets you find places that have the features you are looking for and to see where to take action.

1. Find a feature—People use maps to see where or what an individual feature is.
2. Finding patterns—By looking at the distribution of features on the map instead of just an individual feature, you can see patterns emerge.

What do you need to use GIS?
A full GIS, or geographic information system, requires:

• Hardware (computers and peripherals)
• Software
• Data

AND analysis methods for interpreting the results generated by the GIS.

GIS Software:

GIS software provides the functions and tools needed to store, analyze, and display information about places. The key components of GIS software are

• Tools for entering and manipulating geographic information such as addresses or political boundaries
• A database management system (DBMS)
• Tools that create intelligent digital maps you can analyze, query for more information, or print for presentation
• An easy-to-use graphical user interface (GUI)

GIS software ranges from low-end business-mapping software appropriate for displaying sales territories to high-end software capable of managing and studying large protected natural areas. 

Links to Data Sources:

A GIS can use data from a wide range of proprietary and standard map and graphics file formats, images, CAD files, spreadsheets, relational databases, and many more sources. Data is free or fee-based and comes from commercial, nonprofit, educational, and governmental sources; other GIS software users; as well as your own organization. The following links provide a good start for finding data for your needs:

Census Watch
The Census Watch portal provides immediate access to the most recent information on Census related data resources, redistricting, on-line GIS mapping, education and training, as well as news and articles.

Geospatial Data Clearinghouse
Search more than 100 spatial data servers from different organizations through a single interface created by the U.S. Federal Geographic Data Committee.

Geography Network
The Geography Network is a collaborative, multiparticipant system for publishing, sharing, and using digital geographic information on the Internet.

GeoCommunity Data Depot
This site offers free data from all over the world, or you can pay a fee for a custom-cut CD.

GIS Jump Station
Many of the sites listed offer data either for download or for sale. who can do the work and master the content with little outside support.

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